While working on the new version of the code for SCHED_SPORADIC I
noticed something strange in the present throttling mechanism. More
specifically in the throttling timer handler in sched_rt.c
(do_sched_rt_period_timer()) and in rt_rq_enqueue().
The problem is that, when unthrottling a runqueue, rt_rq_enqueue() only
asks for rescheduling if the runqueue has a sched_entity associated to
it (i.e., rt_rq->rt_se != NULL).
Now, if the runqueue is the root rq (which has a rt_se = NULL)
rescheduling does not take place, and it is delayed to some undefined
instant in the future.
This imply some random bandwidth usage by the RT tasks under throttling.
For instance, setting rt_runtime_us/rt_period_us = 950ms/1000ms an RT
task will get less than 95%. In our tests we got something varying
between 70% to 95%.
Using smaller time values, e.g., 95ms/100ms, things are even worse, and
I can see values also going down to 20-25%!!
The tests we performed are simply running 'yes' as a SCHED_FIFO task,
and checking the CPU usage with top, but we can investigate thoroughly
if you think it is needed.
Things go much better, for us, with the attached patch... Don't know if
it is the best approach, but it solved the issue for us.
Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Michael Trimarchi <trimarchimichael@yahoo.it>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: jiffies increment too fast.
Hugh Dickins noted that with NOHZ=n and HIGHRES=n jiffies get
incremented too fast. The reason is a wrong check in the broadcast
enter/exit code, which keeps the local apic timer in periodic mode
when the switch happens.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This fixes a warning on latest -tip:
kernel/cpuset.c: Dans la fonction «scan_for_empty_cpusets» :
kernel/cpuset.c:1932: attention : passing argument 1 of «list_add_tail» discards qualifiers from pointer target type
Actually the struct cpuset *root passed in parameter to scan_for_empty_cpusets
is not supposed to be const since an entry is added on the tail of its list.
Just correct the qualifier.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Last -tip gives this warning:
kernel/softirq.c: Dans la fonction «__do_softirq» :
kernel/softirq.c:216: attention : format «%ld» expects type «long int», but argument 2 has type «int»
This patch corrects the format type, and a small mistake in the "softirq" word.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix the !CONFIG_RCU_CPU_STALL_DETECTOR path:
kernel/rcuclassic.c: In function '__rcu_pending':
kernel/rcuclassic.c:609: error: too few arguments to function 'check_cpu_stall'
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds stalled-CPU detection to Classic RCU. This capability
is enabled by a new config variable CONFIG_RCU_CPU_STALL_DETECTOR, which
defaults disabled.
This is a debugging feature to detect infinite loops in kernel code, not
something that non-kernel-hackers would be expected to care about.
This feature can detect looping CPUs in !PREEMPT builds and looping CPUs
with preemption disabled in PREEMPT builds. This is essentially a port of
this functionality from the treercu patch, replacing the stall debug patch
that is already in tip/core/rcu (commit 67182ae1c4).
The changes from the patch in tip/core/rcu include making the config
variable name match that in treercu, changing from seconds to jiffies to
avoid spurious warnings, and printing a boot message when this feature
is enabled.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Found by static checker (http://repo.or.cz/w/smatch.git).
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
if a preempt count leaks out of a softirq handler it can be very hard
to figure it out. Add a debug check for this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Genirq hasn't previously recorded the trigger type used by any given IRQ,
although some irq_chip support has done so. That data can be useful when
troubleshooting. This patch records it in the relevant irq_desc.status
bits, and improves consistency between the two driver-visible calls
affected:
- Make set_irq_type() usage match request_irq() usage:
* IRQ_TYPE_NONE should be a NOP; succeed, so irq_chip methods
won't have to handle that case any more (many do it wrong).
* IRQ_TYPE_PROBE is ignored; any buggy out-of-tree callers
might need to switch over to the real IRQ probing code.
* emit the same diagnostics (from shared utility code)
- Their kerneldoc now reflects usage:
* request_irq() flags include IRQF_TRIGGER_* to specify
active edge(s)/level ... docs previously omitted that
* set_irq_type() is declared in <linux/irq.h> so callers
should use the (bit-equivalent) IRQ_TYPE_* symbols there
Also: adds a warning about shared IRQs that don't end up using the
requested trigger mode; and fix an unrelated "sparse" warning.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
hrtimer: prevent migration of per CPU hrtimers
hrtimer: mark migration state
hrtimer: fix migration of CB_IRQSAFE_NO_SOFTIRQ hrtimers
hrtimer: migrate pending list on cpu offline
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This patch does following:
o Removes unused variable and argument "rq".
o Optimizes one of the "if" conditions in wake_affine() - i.e. if
"balanced" is true, we need not do rest of the calculations in the
condition.
o If this cpu is same as the previous cpu (on which woken up task
was running when it went to sleep), no need to call wake_affine at all.
Signed-off-by: Amit K Arora <aarora@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds the CONFIG_FILE_LOCKING option which allows to remove
support for advisory locks. With this patch enabled, the flock()
system call, the F_GETLK, F_SETLK and F_SETLKW operations of fcntl()
and NFS support are disabled. These features are not necessarly needed
on embedded systems. It allows to save ~11 Kb of kernel code and data:
text data bss dec hex filename
1125436 118764 212992 1457192 163c28 vmlinux.old
1114299 118564 212992 1445855 160fdf vmlinux
-11137 -200 0 -11337 -2C49 +/-
This patch has originally been written by Matt Mackall
<mpm@selenic.com>, and is part of the Linux Tiny project.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: matthew@wil.cx
Cc: linux-fsdevel@vger.kernel.org
Cc: mpm@selenic.com
Cc: akpm@linux-foundation.org
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
There's a race between mm->owner assignment and swapoff, more easily
seen when task slab poisoning is turned on. The condition occurs when
try_to_unuse() runs in parallel with an exiting task. A similar race
can occur with callers of get_task_mm(), such as /proc/<pid>/<mmstats>
or ptrace or page migration.
CPU0 CPU1
try_to_unuse
looks at mm = task0->mm
increments mm->mm_users
task 0 exits
mm->owner needs to be updated, but no
new owner is found (mm_users > 1, but
no other task has task->mm = task0->mm)
mm_update_next_owner() leaves
mmput(mm) decrements mm->mm_users
task0 freed
dereferencing mm->owner fails
The fix is to notify the subsystem via mm_owner_changed callback(),
if no new owner is found, by specifying the new task as NULL.
Jiri Slaby:
mm->owner was set to NULL prior to calling cgroup_mm_owner_callbacks(), but
must be set after that, so as not to pass NULL as old owner causing oops.
Daisuke Nishimura:
mm_update_next_owner() may set mm->owner to NULL, but mem_cgroup_from_task()
and its callers need to take account of this situation to avoid oops.
Hugh Dickins:
Lockdep warning and hang below exec_mmap() when testing these patches.
exit_mm() up_reads mmap_sem before calling mm_update_next_owner(),
so exec_mmap() now needs to do the same. And with that repositioning,
there's now no point in mm_need_new_owner() allowing for NULL mm.
Reported-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Impact: per CPU hrtimers can be migrated from a dead CPU
The hrtimer code has no knowledge about per CPU timers, but we need to
prevent the migration of such timers and warn when such a timer is
active at migration time.
Explicitely mark the timers as per CPU and use a more understandable
mode descriptor for the interrupts safe unlocked callback mode, which
is used by hrtimer_sleeper and the scheduler code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: during migration active hrtimers can be seen as inactive
The migration code removes the hrtimers from the queues of the dead
CPU and sets the state temporary to INACTIVE. The enqueue code sets it
to ACTIVE/PENDING again.
Prevent that the wrong state can be seen by using a separate migration
state bit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: Stale timers after a CPU went offline.
commit 37bb6cb409
hrtimer: unlock hrtimer_wakeup
changed the hrtimer sleeper callback mode to CB_IRQSAFE_NO_SOFTIRQ due
to locking problems. A result of this change is that when enqueue is
called for an already expired hrtimer the callback function is not
longer called directly from the enqueue code. The normal callers have
been fixed in the code, but the migration code which moves hrtimers
from a dead CPU to a live CPU was not made aware of this.
This can be fixed by checking the timer state after the call to
enqueue in the migration code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: hrtimers which are on the pending list are not migrated at cpu
offline and can be stale forever
Add the pending list migration when CONFIG_HIGH_RES_TIMERS is enabled
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
- fix UP lockup
- another set of UP/SMP cleanups and simplifications
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On the x86 arch, user space single step exceptions should be ignored
if they occur in the kernel space, such as ptrace stepping through a
system call.
First check if it is kgdb that is executing a single step, then ensure
it is not an accidental traversal into the user space, while in kgdb,
any other time the TIF_SINGLESTEP is set, kgdb should ignore the
exception.
On x86, arm, mips and powerpc, the kgdb_contthread usage was
inconsistent with the way single stepping is implemented in the kgdb
core. The arch specific stub should always set the
kgdb_cpu_doing_single_step correctly if it is single stepping. This
allows kgdb to correctly process an instruction steps if ptrace
happens to be requesting an instruction step over a system call.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
On the ARM architecture, kgdb will crash the kernel if the last byte
of valid memory is written due to a flush_icache_range flushing
beyond the memory boundary.
Signed-off-by: Atsuo Igarashi <atsuo_igarashi@tripeaks.co.jp>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
fix this build error:
kernel/resource.c: In function 'iomem_map_sanity_check':
kernel/resource.c:842: error: implicit declaration of function 'r_next'
kernel/resource.c:842: warning: assignment makes pointer from integer without a cast
r_next() was only available if CONFIG_PROCFS was enabled.
and fix this build warning:
kernel/resource.c:855: warning: format '%llx' expects type 'long long unsigned int', but argument 2 has type 'resource_size_t'
kernel/resource.c:855: warning: format '%llx' expects type 'long long unsigned int', but argument 3 has type 'long unsigned int'
kernel/resource.c:855: warning: format '%llx' expects type 'long long unsigned int', but argument 4 has type 'resource_size_t'
kernel/resource.c:855: warning: format '%llx' expects type 'long long unsigned int', but argument 5 has type 'resource_size_t'
resource_t can be 32 bits.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Go through the iomem resource tree to check if any of the ioremap()
requests span more than any slot in the iomem resource tree and do
a WARN_ON() if we hit this check.
This will raise a red-flag, if some driver is mapping more than what
is needed. And hopefully identify possible corruptions much earlier.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
cfs_rq->tasks list is used by the load balancer to iterate
over all the tasks. Currently it holds all the entities
(both task and group entities) because of which there is
a need to check for group entities explicitly during load
balancing. This patch changes the cfs_rq->tasks list to
hold only task entities.
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change PPM_SCALE_INV_SHIFT so that it doesn't throw away any input bits
(19 is the amount of the factor 2 in PPM_SCALE), the output frequency
can then be calculated back to its input value, as the inverse divide
produce a slightly larger value, which is then correctly rounded by the
final shift.
Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Due to a rounding problem during a clock update it's possible for readers
to observe the clock jumping back by 1nsec. The following simplified
example demonstrates the problem:
cycle xtime
0 0
1000 999999.6
2000 1999999.2
3000 2999998.8
...
1500 = 1499999.4
= 0.0 + 1499999.4
= 999999.6 + 499999.8
When reading the clock only the full nanosecond part is used, while
timekeeping internally keeps nanosecond fractions. If the clock is now
updated at cycle 1500 here, a nanosecond is missing due to the truncation.
The simple fix is to round up the xtime value during the update, this also
changes the distance to the reference time, but the adjustment will
automatically take care that it stays under control.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This is a change that makes the 11-minute RTC update be run in the process
context. This is so that update_persistent_clock() can sleep, which may
be required for certain types of RTC hardware -- most notably I2C devices.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cleanup. Imho makes the code much more understandable. At least this
patch lessens both the source and compiled code.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
lock_timer() checks that the timer found by idr_find(timer_id) has ->it_id
== timer_id. This buys nothing. This check can fail only if
sys_timer_create() unlocked idr_lock after idr_get_new(), but didn't set
->it_id = new_timer_id yet. But in that case ->it_process == NULL so
lock_timer() can't succeed anyway.
Also remove a couple of unneeded typecasts.
Note that with or without this patch we have a small problem.
sys_timer_create() doesn't ensure that the result of setting (say)
->it_sigev_notify must be visible if lock_timer() succeeds.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
With the recent changes ->it_sigev_signo and ->it_sigev_value are only
used in sys_timer_create(), kill them.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cleanup.
- sys_timer_create() is big and complicated. The code above the "out:"
label relies on the fact that "error" must be == 0. This is not very
robust, make the code more explicit. Remove the unneeded initialization
of error.
- If idr_get_new() succeeds (as it normally should), we check the returned
value twice. Move the "-EAGAIN" check under "if (error)".
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
posix_timer_event() always populates timer->sigq with the same numbers,
move this code into sys_timer_create().
Note that with this patch we can kill it_sigev_signo and it_sigev_value.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
- Change the code to do rcu_read_lock() instead of taking tasklist_lock,
it is safe to get_task_struct(p) if p was found under RCU.
However, now we must not use process's sighand/signal, they may be NULL.
We can use current->sighand/signal instead, this "process" must belong
to the current's thread-group.
- Factor out the common code for 2 "if (timer_event_spec)" branches, the
!timer_event_spec case can use current too.
- use spin_lock_irq() instead of _irqsave(), kill "flags".
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
sys_timer_create() return -EINVAL if the target thread has PF_EXITING.
This doesn't really make sense, the sub-thread can die right after unlock.
And in fact, this is just wrong. Without SIGEV_THREAD_ID good_sigevent()
returns ->group_leader, and it is very possible that the leader is already
dead. This is OK, we shouldn't return the error in this case.
Remove this check and the comment. Note that the "process" was found
under tasklist_lock, it must have ->sighand != NULL.
Also, remove a couple of unneeded initializations.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Change the code to get/put timer->it_process regardless of
SIGEV_THREAD_ID. This streamlines the create/destroy paths and allows us
to simplify the usage of exit_itimers() in de_thread().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
posix_timer_event() drops SIGEV_THREAD_ID and switches to ->group_leader
if send_sigqueue() fails.
This is not very useful and doesn't work reliably. send_sigqueue() can
only fail if ->it_process is dead. But it can die before it dequeues the
SI_TIMER signal, in that case the timer stops anyway.
Remove this code. I guess it was needed a long ago to ensure that the
timer is not destroyed when when its creator thread dies.
Q: perhaps it makes sense to change sys_timer_settime() to return an error
if ->it_process is dead?
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: mingo@elte.hu
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
timers: fix build error in !oneshot case
x86: c1e_idle: don't mark TSC unstable if CPU has invariant TSC
x86: prevent C-states hang on AMD C1E enabled machines
clockevents: prevent mode mismatch on cpu online
clockevents: check broadcast device not tick device
clockevents: prevent stale tick_next_period for onlining CPUs
x86: prevent stale state of c1e_mask across CPU offline/online
clockevents: prevent cpu online to interfere with nohz
A segmentation fault can occur in kimage_add_entry in kexec.c when loading
a kernel image into memory. The fault occurs because a page is requested
by calling kimage_alloc_page with gfp_mask GFP_KERNEL and the function may
actually return a page with gfp_mask GFP_HIGHUSER. The high mem page is
returned because it was swapped with the kernel page due to the kernel
page being a page that will shortly be copied to.
This patch ensures that kimage_alloc_page returns a page that was created
with the correct gfp flags.
I have verified the change and fixed the whitespace damage of the original
patch. Jonathan did a great job of tracking this down after he hit the
problem. -- Eric
Signed-off-by: Jonathan Steel <jon.steel@esentire.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We should set the buddy even though we might already have the
TIF_RESCHED flag set.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
While playing around with it, I noticed we missed some sanity checks.
Also add some comments while we're there.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should not only correct the increment for the initial group, but should
be consistent and do so for all the groups we encounter.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Rework the wakeup preemption to work on real runtime instead of
the virtual runtime. This greatly simplifies the code.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This is the second resubmission of the posix timer rework patch, posted
a few days ago.
This includes the changes from the previous resubmittion, which addressed
Oleg Nesterov's comments, removing the RCU stuff from the patch and
un-inlining the thread_group_cputime() function for SMP.
In addition, per Ingo Molnar it simplifies the UP code, consolidating much
of it with the SMP version and depending on lower-level SMP/UP handling to
take care of the differences.
It also cleans up some UP compile errors, moves the scheduler stats-related
macros into kernel/sched_stats.h, cleans up a merge error in
kernel/fork.c and has a few other minor fixes and cleanups as suggested
by Oleg and Ingo. Thanks for the review, guys.
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel/time/tick-common.c: In function ‘tick_setup_periodic’:
kernel/time/tick-common.c:113: error: implicit declaration of function ‘tick_broadcast_oneshot_active’
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: timer hang on CPU online observed on AMD C1E systems
When a CPU is brought online then the broadcast machinery can
be in the one shot state already. Check this and setup the timer
device of the new CPU in one shot mode so the broadcast code
can pick up the next_event value correctly.
Another AMD C1E oddity, as we switch to broadcast immediately and
not after the full bring up via the ACPI cpu idle code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: Possible hang on CPU online observed on AMD C1E machines.
The broadcast setup code looks at the mode of the tick device to
determine whether it needs to be shut down or setup. This is wrong
when the broadcast mode is set to one shot already. This can happen
when a CPU is brought online as it goes through the periodic setup
first.
The problem went unnoticed as sane systems do not call into that code
before the switch to one shot for the clock event device happens.
The AMD C1E idle routine switches over immediately and thereby shuts
down the just setup device before the first interrupt happens.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: possible hang on CPU onlining in timer one shot mode.
The tick_next_period variable is only used during boot on nohz/highres
enabled systems, but for CPU onlining it needs to be maintained when
the per cpu clock events device operates in one shot mode.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: rare hang which can be triggered on CPU online.
tick_do_timer_cpu keeps track of the CPU which updates jiffies
via do_timer. The value -1 is used to signal, that currently no
CPU is doing this. There are two cases, where the variable can
have this state:
boot:
necessary for systems where the boot cpu id can be != 0
nohz long idle sleep:
When the CPU which did the jiffies update last goes into
a long idle sleep it drops the update jiffies duty so
another CPU which is not idle can pick it up and keep
jiffies going.
Using the same value for both situations is wrong, as the CPU online
code can see the -1 state when the timer of the newly onlined CPU is
setup. The setup for a newly onlined CPU goes through periodic mode
and can pick up the do_timer duty without being aware of the nohz /
highres mode of the already running system.
Use two separate states and make them constants to avoid magic
numbers confusion.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
kernel/rcuclassic.c:564:18: warning: symbol 'flags' shadows an earlier one
kernel/rcuclassic.c:527:16: originally declared here
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
- Add some comments to try to make the ifdef puzzle a bit clearer
- Explicitly inline one of the three init_hrtick() implementations.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LD kernel/built-in.o
WARNING: kernel/built-in.o(.text+0x326): Section mismatch in reference
from the function init_hrtick() to the variable
.cpuinit.data:hotplug_hrtick_nb.8
The function init_hrtick() references
the variable __cpuinitdata hotplug_hrtick_nb.8.
This is often because init_hrtick lacks a __cpuinitdata
annotation or the annotation of hotplug_hrtick_nb.8 is wrong.
Signed-off-by: Md.Rakib H. Mullick <rakib.mullick@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
load_balance_fair() calls rcu_read_lock() but then traverses the list
using the regular list traversal routine. This patch converts the
list traversal to use the _rcu version.
Signed-off-by: Chris Friesen <cfriesen@nortel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Lin Ming reported a 10% OLTP regression against 2.6.27-rc4.
The difference seems to come from different preemption agressiveness,
which affects the cache footprint of the workload and its effective
cache trashing.
Aggresively preempt a task if its avg overlap is very small, this should
avoid the task going to sleep and find it still running when we schedule
back to it - saving a wakeup.
Reported-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Zijlstra noticed this 8 months ago and I just noticed
it again.
hrtimer_clock_base::get_softirq_time() is currently unused
in the entire tree. In fact, looking at the logs, it appears
as if it was never used. Remove it.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: fix deadlock in setting scheduler parameter to zero
sched: fix 2.6.27-rc5 couldn't boot on tulsa machine randomly
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
clockevents: make device shutdown robust
clocksource, acpi_pm.c: fix check for monotonicity
clockevents: remove WARN_ON which was used to gather information
The device shut down does not cleanup the next_event variable of the
clock event device. So when the device is reactivated the possible
stale next_event value can prevent the device to be reprogrammed as it
claims to wait on a event already.
This is the root cause of the resurfacing suspend/resume problem,
where systems need key press to come back to life.
Fix this by setting next_event to KTIME_MAX when the device is shut
down. Use a separate function for shutdown which takes care of that
and only keep the direct set mode call in the broadcast code, where we
can not touch the next_event value.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
fix:
kernel/fork.c:843: error: ‘struct signal_struct’ has no member named ‘sum_sched_runtime’
kernel/irq/handle.c:117: warning: ‘sparse_irq_lock’ defined but not used
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Overview
This patch reworks the handling of POSIX CPU timers, including the
ITIMER_PROF, ITIMER_VIRT timers and rlimit handling. It was put together
with the help of Roland McGrath, the owner and original writer of this code.
The problem we ran into, and the reason for this rework, has to do with using
a profiling timer in a process with a large number of threads. It appears
that the performance of the old implementation of run_posix_cpu_timers() was
at least O(n*3) (where "n" is the number of threads in a process) or worse.
Everything is fine with an increasing number of threads until the time taken
for that routine to run becomes the same as or greater than the tick time, at
which point things degrade rather quickly.
This patch fixes bug 9906, "Weird hang with NPTL and SIGPROF."
Code Changes
This rework corrects the implementation of run_posix_cpu_timers() to make it
run in constant time for a particular machine. (Performance may vary between
one machine and another depending upon whether the kernel is built as single-
or multiprocessor and, in the latter case, depending upon the number of
running processors.) To do this, at each tick we now update fields in
signal_struct as well as task_struct. The run_posix_cpu_timers() function
uses those fields to make its decisions.
We define a new structure, "task_cputime," to contain user, system and
scheduler times and use these in appropriate places:
struct task_cputime {
cputime_t utime;
cputime_t stime;
unsigned long long sum_exec_runtime;
};
This is included in the structure "thread_group_cputime," which is a new
substructure of signal_struct and which varies for uniprocessor versus
multiprocessor kernels. For uniprocessor kernels, it uses "task_cputime" as
a simple substructure, while for multiprocessor kernels it is a pointer:
struct thread_group_cputime {
struct task_cputime totals;
};
struct thread_group_cputime {
struct task_cputime *totals;
};
We also add a new task_cputime substructure directly to signal_struct, to
cache the earliest expiration of process-wide timers, and task_cputime also
replaces the it_*_expires fields of task_struct (used for earliest expiration
of thread timers). The "thread_group_cputime" structure contains process-wide
timers that are updated via account_user_time() and friends. In the non-SMP
case the structure is a simple aggregator; unfortunately in the SMP case that
simplicity was not achievable due to cache-line contention between CPUs (in
one measured case performance was actually _worse_ on a 16-cpu system than
the same test on a 4-cpu system, due to this contention). For SMP, the
thread_group_cputime counters are maintained as a per-cpu structure allocated
using alloc_percpu(). The timer functions update only the timer field in
the structure corresponding to the running CPU, obtained using per_cpu_ptr().
We define a set of inline functions in sched.h that we use to maintain the
thread_group_cputime structure and hide the differences between UP and SMP
implementations from the rest of the kernel. The thread_group_cputime_init()
function initializes the thread_group_cputime structure for the given task.
The thread_group_cputime_alloc() is a no-op for UP; for SMP it calls the
out-of-line function thread_group_cputime_alloc_smp() to allocate and fill
in the per-cpu structures and fields. The thread_group_cputime_free()
function, also a no-op for UP, in SMP frees the per-cpu structures. The
thread_group_cputime_clone_thread() function (also a UP no-op) for SMP calls
thread_group_cputime_alloc() if the per-cpu structures haven't yet been
allocated. The thread_group_cputime() function fills the task_cputime
structure it is passed with the contents of the thread_group_cputime fields;
in UP it's that simple but in SMP it must also safely check that tsk->signal
is non-NULL (if it is it just uses the appropriate fields of task_struct) and,
if so, sums the per-cpu values for each online CPU. Finally, the three
functions account_group_user_time(), account_group_system_time() and
account_group_exec_runtime() are used by timer functions to update the
respective fields of the thread_group_cputime structure.
Non-SMP operation is trivial and will not be mentioned further.
The per-cpu structure is always allocated when a task creates its first new
thread, via a call to thread_group_cputime_clone_thread() from copy_signal().
It is freed at process exit via a call to thread_group_cputime_free() from
cleanup_signal().
All functions that formerly summed utime/stime/sum_sched_runtime values from
from all threads in the thread group now use thread_group_cputime() to
snapshot the values in the thread_group_cputime structure or the values in
the task structure itself if the per-cpu structure hasn't been allocated.
Finally, the code in kernel/posix-cpu-timers.c has changed quite a bit.
The run_posix_cpu_timers() function has been split into a fast path and a
slow path; the former safely checks whether there are any expired thread
timers and, if not, just returns, while the slow path does the heavy lifting.
With the dedicated thread group fields, timers are no longer "rebalanced" and
the process_timer_rebalance() function and related code has gone away. All
summing loops are gone and all code that used them now uses the
thread_group_cputime() inline. When process-wide timers are set, the new
task_cputime structure in signal_struct is used to cache the earliest
expiration; this is checked in the fast path.
Performance
The fix appears not to add significant overhead to existing operations. It
generally performs the same as the current code except in two cases, one in
which it performs slightly worse (Case 5 below) and one in which it performs
very significantly better (Case 2 below). Overall it's a wash except in those
two cases.
I've since done somewhat more involved testing on a dual-core Opteron system.
Case 1: With no itimer running, for a test with 100,000 threads, the fixed
kernel took 1428.5 seconds, 513 seconds more than the unfixed system,
all of which was spent in the system. There were twice as many
voluntary context switches with the fix as without it.
Case 2: With an itimer running at .01 second ticks and 4000 threads (the most
an unmodified kernel can handle), the fixed kernel ran the test in
eight percent of the time (5.8 seconds as opposed to 70 seconds) and
had better tick accuracy (.012 seconds per tick as opposed to .023
seconds per tick).
Case 3: A 4000-thread test with an initial timer tick of .01 second and an
interval of 10,000 seconds (i.e. a timer that ticks only once) had
very nearly the same performance in both cases: 6.3 seconds elapsed
for the fixed kernel versus 5.5 seconds for the unfixed kernel.
With fewer threads (eight in these tests), the Case 1 test ran in essentially
the same time on both the modified and unmodified kernels (5.2 seconds versus
5.8 seconds). The Case 2 test ran in about the same time as well, 5.9 seconds
versus 5.4 seconds but again with much better tick accuracy, .013 seconds per
tick versus .025 seconds per tick for the unmodified kernel.
Since the fix affected the rlimit code, I also tested soft and hard CPU limits.
Case 4: With a hard CPU limit of 20 seconds and eight threads (and an itimer
running), the modified kernel was very slightly favored in that while
it killed the process in 19.997 seconds of CPU time (5.002 seconds of
wall time), only .003 seconds of that was system time, the rest was
user time. The unmodified kernel killed the process in 20.001 seconds
of CPU (5.014 seconds of wall time) of which .016 seconds was system
time. Really, though, the results were too close to call. The results
were essentially the same with no itimer running.
Case 5: With a soft limit of 20 seconds and a hard limit of 2000 seconds
(where the hard limit would never be reached) and an itimer running,
the modified kernel exhibited worse tick accuracy than the unmodified
kernel: .050 seconds/tick versus .028 seconds/tick. Otherwise,
performance was almost indistinguishable. With no itimer running this
test exhibited virtually identical behavior and times in both cases.
In times past I did some limited performance testing. those results are below.
On a four-cpu Opteron system without this fix, a sixteen-thread test executed
in 3569.991 seconds, of which user was 3568.435s and system was 1.556s. On
the same system with the fix, user and elapsed time were about the same, but
system time dropped to 0.007 seconds. Performance with eight, four and one
thread were comparable. Interestingly, the timer ticks with the fix seemed
more accurate: The sixteen-thread test with the fix received 149543 ticks
for 0.024 seconds per tick, while the same test without the fix received 58720
for 0.061 seconds per tick. Both cases were configured for an interval of
0.01 seconds. Again, the other tests were comparable. Each thread in this
test computed the primes up to 25,000,000.
I also did a test with a large number of threads, 100,000 threads, which is
impossible without the fix. In this case each thread computed the primes only
up to 10,000 (to make the runtime manageable). System time dominated, at
1546.968 seconds out of a total 2176.906 seconds (giving a user time of
629.938s). It received 147651 ticks for 0.015 seconds per tick, still quite
accurate. There is obviously no comparable test without the fix.
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
After the patch:
commit 0b2f630a28
Author: Miao Xie <miaox@cn.fujitsu.com>
Date: Fri Jul 25 01:47:21 2008 -0700
cpusets: restructure the function update_cpumask() and update_nodemask()
It might happen that 'echo 0 > /cpuset/sub/cpus' returned failure but 'cpus'
has been changed, because cpus was changed before calling heap_init() which
may return -ENOMEM.
This patch restores the orginal behavior.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On my tulsa x86-64 machine, kernel 2.6.25-rc5 couldn't boot randomly.
Basically, function __enable_runtime forgets to reset rt_rq->rt_throttled
to 0. When every cpu is up, per-cpu migration_thread is created and it runs
very fast, sometimes to mark the corresponding rt_rq->rt_throttled to 1 very
quickly. After all cpus are up, with below calling chain:
sched_init_smp => arch_init_sched_domains => build_sched_domains => ...
=> cpu_attach_domain => rq_attach_root => set_rq_online => ...
=> _enable_runtime
_enable_runtime is called against every rt_rq again, so rt_rq->rt_time is
reset to 0, but rt_rq->rt_throttled might be still 1. Later on function
do_sched_rt_period_timer couldn't reset it, and all RT tasks couldn't be
scheduled to run on that cpu. here is RT task migration_thread which is
woken up when a task is migrated to another cpu.
Below patch fixes it against 2.6.27-rc5.
Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The issue of the endless reprogramming loop due to a too small
min_delta_ns was fixed with the previous updates of the clock events
code, but we had no information about the spread of this problem. I
added a WARN_ON to get automated information via kerneloops.org and to
get some direct reports, which allowed me to analyse the affected
machines.
The WARN_ON has served its purpose and would be annoying for a release
kernel. Remove it and just keep the information about the increase of
the min_delta_ns value.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: arch_reinit_sched_domains() must destroy domains to force rebuild
sched, cpuset: rework sched domains and CPU hotplug handling (v4)
Right now, there is no notifier that is called on a new cpu, before the new
cpu begins processing interrupts/softirqs.
Various kernel function would need that notification, e.g. kvm works around
by calling smp_call_function_single(), rcu polls cpu_online_map.
The patch adds a CPU_STARTING notification. It also adds a helper function
that sends the message to all cpu_chain handlers.
Tested on x86-64.
All other archs are untested. Especially on sparc, I'm not sure if I got
it right.
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch clarifies usage of irq_chip->startup() callback:
1. The "if (startup) startup(); else enabled();" code in setup_irq()
is unnecessary, as startup() falls back to enabled() via
default callbacks, set by irq_chip_set_defaults().
2. When using set_irq_chained_handler() the startup() was never called,
which is not good at all... Fixed. And again - when startup() is not
defined the call will fall back to enable() than to unmask() via
default callbacks.
Signed-off-by: Pawel Moll <pawel.moll@st.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We don't need whole 32 of them, only NR_SOFTIRQS.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
What I realized recently is that calling rebuild_sched_domains() in
arch_reinit_sched_domains() by itself is not enough when cpusets are enabled.
partition_sched_domains() code is trying to avoid unnecessary domain rebuilds
and will not actually rebuild anything if new domain masks match the old ones.
What this means is that doing
echo 1 > /sys/devices/system/cpu/sched_mc_power_savings
on a system with cpusets enabled will not take affect untill something changes
in the cpuset setup (ie new sets created or deleted).
This patch fixes restore correct behaviour where domains must be rebuilt in
order to enable MC powersaving flags.
Test on quad-core Core2 box with both CONFIG_CPUSETS and !CONFIG_CPUSETS.
Also tested on dual-core Core2 laptop. Lockdep is happy and things are working
as expected.
Signed-off-by: Max Krasnyansky <maxk@qualcomm.com>
Tested-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When a cpu is taken offline, the CPU_DYING notifiers are called on the
dying cpu. According to <linux/notifiers.h>, the cpu should be "not
running any task, not handling interrupts, soon dead".
For the current implementation, this is not true:
- __cpu_disable can fail. If it fails, then the cpu will remain alive
and happy.
- At least on x86, __cpu_disable() briefly enables the local interrupts
to handle any outstanding interrupts.
What about moving CPU_DYING down a few lines, behind the __cpu_disable()
line?
There are only two CPU_DYING handlers in the kernel right now: one in
kvm, one in the scheduler. Both should work with the patch applied
[and: I'm not sure if either one handles a failing __cpu_disable()]
The patch survives simple offlining a cpu. kvm untested due to lack
of a test setup.
Signed-off-By: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The __load_balance_iterator() returns a NULL when there's only one
sched_entity which is a task. It is caused by the following code-path.
/* Skip over entities that are not tasks */
do {
se = list_entry(next, struct sched_entity, group_node);
next = next->next;
} while (next != &cfs_rq->tasks && !entity_is_task(se));
if (next == &cfs_rq->tasks)
return NULL;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This will return NULL even when se is a task.
As a side-effect, there was a regression in sched_mc behavior since 2.6.25,
since iter_move_one_task() when it calls load_balance_start_fair(),
would not get any tasks to move!
Fix this by checking if the last entity was a task or not.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We have a bug in the calculation of the next jiffie to trigger the RTC
synchronisation. The aim here is to run sync_cmos_clock() as close as
possible to the middle of a second. Which means we want this function to
be called less than or equal to half a jiffie away from when now.tv_nsec
equals 5e8 (500000000).
If this is not the case for a given call to the function, for this purpose
instead of updating the RTC we calculate the offset in nanoseconds to the
next point in time where now.tv_nsec will be equal 5e8. The calculated
offset is then converted to jiffies as these are the unit used by the
timer.
Hovewer timespec_to_jiffies() used here uses a ceil()-type rounding mode,
where the resulting value is rounded up. As a result the range of
now.tv_nsec when the timer will trigger is from 5e8 to 5e8 + TICK_NSEC
rather than the desired 5e8 - TICK_NSEC / 2 to 5e8 + TICK_NSEC / 2.
As a result if for example sync_cmos_clock() happens to be called at the
time when now.tv_nsec is between 5e8 + TICK_NSEC / 2 and 5e8 to 5e8 +
TICK_NSEC, it will simply be rescheduled HZ jiffies later, falling in the
same range of now.tv_nsec again. Similarly for cases offsetted by an
integer multiple of TICK_NSEC.
This change addresses the problem by subtracting TICK_NSEC / 2 from the
nanosecond offset to the next point in time where now.tv_nsec will be
equal 5e8, effectively shifting the following rounding in
timespec_to_jiffies() so that it produces a rounded-to-nearest result.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I found that 2.6.27-rc5-mm1 does not compile with gcc 3.4.6.
The error is:
CC kernel/sched.o
kernel/sched.c: In function `start_rt_bandwidth':
kernel/sched.c:208: sorry, unimplemented: inlining failed in call to 'rt_bandwidth_enabled': function body not available
kernel/sched.c:214: sorry, unimplemented: called from here
make[1]: *** [kernel/sched.o] Error 1
make: *** [kernel] Error 2
It seems that the gcc 3.4.6 requires full inline definition before first usage.
The patch below fixes the compilation problem.
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> (if needed>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Until the C1E patches arrived there where no users of periodic broadcast
before switching to oneshot mode. Now we need to trigger a possible
waiter for a periodic broadcast when switching to oneshot mode.
Otherwise we can starve them for ever.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Spencer reported a problem where utime and stime were going negative despite
the fixes in commit b27f03d4bd. The suspected
reason for the problem is that signal_struct maintains it's own utime and
stime (of exited tasks), these are not updated using the new task_utime()
routine, hence sig->utime can go backwards and cause the same problem
to occur (sig->utime, adds tsk->utime and not task_utime()). This patch
fixes the problem
TODO: using max(task->prev_utime, derived utime) works for now, but a more
generic solution is to implement cputime_max() and use the cputime_gt()
function for comparison.
Reported-by: spencer@bluehost.com
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If HLT stops the TSC, we'll fail to account idle time, thereby inflating the
actual process times. Fix this by re-calibrating the clock against GTOD when
leaving nohz mode.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The C1E/HPET bug reports on AMDX2/RS690 systems where tracked down to a
too small value of the HPET minumum delta for programming an event.
The clockevents code needs to enforce an interrupt event on the clock event
device in some cases. The enforcement code was stupid and naive, as it just
added the minimum delta to the current time and tried to reprogram the device.
When the minimum delta is too small, then this loops forever.
Add a sanity check. Allow reprogramming to fail 3 times, then print a warning
and double the minimum delta value to make sure, that this does not happen again.
Use the same function for both tick-oneshot and tick-broadcast code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
While chasing the C1E/HPET bugreports I went through the clock events
code inch by inch and found that the broadcast device can be initialized
and shutdown multiple times. Multiple shutdowns are not critical, but
useless waste of time. Multiple initializations are simply broken. Another
CPU might have the device in use already after the first initialization and
the second init could just render it unusable again.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In tick_oneshot_setup we program the device to the given next_event,
but we do not check the return value. We need to make sure that the
device is programmed enforced so the interrupt handler engine starts
working. Split out the reprogramming function from tick_program_event()
and call it with the device, which was handed in to tick_setup_oneshot().
Set the force argument, so the devices is firing an interrupt.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The reprogramming of the periodic broadcast handler was broken,
when the first programming returned -ETIME. The clockevents code
stores the new expiry value in the clock events device next_event field
only when the programming time has not been elapsed yet. The loop in
question calculates the new expiry value from the next_event value
and therefor never increases.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There is a ordering related problem with clockevents code, due to which
clockevents_register_device() called after tickless/highres switch
will not work. The new clockevent ends up with clockevents_handle_noop as
event handler, resulting in no timer activity.
The problematic path seems to be
* old device already has hrtimer_interrupt as the event_handler
* new clockevent device registers with a higher rating
* tick_check_new_device() is called
* clockevents_exchange_device() gets called
* old->event_handler is set to clockevents_handle_noop
* tick_setup_device() is called for the new device
* which sets new->event_handler using the old->event_handler which is noop.
Change the ordering so that new device inherits the proper handler.
This does not have any issue in normal case as most likely all the clockevent
devices are setup before the highres switch. But, can potentially be affecting
some corner case where HPET force detect happens after the highres switch.
This was a problem with HPET in MSI mode code that we have been experimenting
with.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Andrew Morton noticed that the printk in kernel/resource.c was buggy:
| start and end have type resource_size_t. Such types CANNOT be printed
| unless cast to a known type.
|
| Because there is a %s following an incorrect %lld, the above code will
| crash the machine.
... and it's probably quite unneeded as well, so remove it.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add reserve_region_with_split() to not lose e820 reserved entries if
they overlap with existing IO regions:
with test case by extend 0xe0000000 - 0xeffffff to 0xdd800000 -
we get:
e0000000-efffffff : PCI MMCONFIG 0
e0000000-efffffff : reserved
and in /proc/iomem we get:
found conflict for reserved [dd800000, efffffff], try to reserve with split
__reserve_region_with_split: (PCI Bus #80) [dd000000, ddffffff], res: (reserved) [dd800000, efffffff]
__reserve_region_with_split: (PCI Bus #00) [de000000, dfffffff], res: (reserved) [de000000, efffffff]
initcall pci_subsys_init+0x0/0x121 returned 0 after 381 msecs
in dmesg
various fixes and improvements suggested by Linus.
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should've set refcount on the root sysctl table; otherwise we'll blow
up the first time we get down to zero dynamically registered sysctl
tables.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make PM_QOS and CPU_IDLE play nicer when run with the RT-Preempt kernel.
The purpose of the patch is to remove the spin_lock around the read in the
function pm_qos_requirement - since spinlocks can sleep in -rt and this
function is called from idle.
CPU_IDLE polls the target_value's of some of the pm_qos parameters from
the idle loop causing sleeping locking warnings. Changing the
target_value to an atomic avoids this issue.
Remove the spinlock in pm_qos_requirement by making target_value an atomic
type.
Signed-off-by: mark gross <mgross@linux.intel.com>
Signed-off-by: John Kacur <jkacur@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We don't change pid_ns->child_reaper when the main thread of the
subnamespace init exits. As Robert Rex <robert.rex@exasol.com> pointed
out this is wrong.
Yes, the re-parenting itself works correctly, but if the reparented task
exits it needs ->parent->nsproxy->pid_ns in do_notify_parent(), and if the
main thread is zombie its ->nsproxy was already cleared by
exit_task_namespaces().
Introduce the new function, find_new_reaper(), which finds the new
->parent for the re-parenting and changes ->child_reaper if needed. Kill
the now unneeded exit_child_reaper().
Also move the changing of ->child_reaper from zap_pid_ns_processes() to
find_new_reaper(), this consolidates the games with ->child_reaper and
makes it stable under tasklist_lock.
Addresses http://bugzilla.kernel.org/show_bug.cgi?id=11391
Reported-by: Robert Rex <robert.rex@exasol.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zap_pid_ns_processes() sets pid_ns->child_reaper = NULL, this is wrong.
Yes, we have already killed all tasks in this namespace, and sys_wait4()
doesn't see any child. But this doesn't mean ->children list is empty, we
may have EXIT_DEAD tasks which are not visible to do_wait(). In that case
the subsequent forget_original_parent() will crash the kernel because it
will try to re-parent these tasks to the NULL reaper.
Even if there are no childs, it is not good that forget_original_parent()
uses reaper == NULL.
Change the code to set ->child_reaper = init_pid_ns.child_reaper instead.
We could use pid_ns->parent->child_reaper as well, I think this does not
really matter. These EXIT_DEAD tasks are not visible to the new ->parent
after re-parenting, they will silently do release_task() eventually.
Note that we must change ->child_reaper, otherwise
forget_original_parent() will use reaper == father, and in that case we
will hit the (correct) BUG_ON(!list_empty(&father->children)).
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The recent commit 16d9679f33caf7e683471647d1472bfe133d858 changed
check_hung_task() to filter out the TASK_KILLABLE tasks. We can
move this check to the caller which has to test t->state anyway.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix kernel-doc warning for new function:
Warning(linux-2.6.27-rc5-git2//kernel/resource.c:448): No description found for parameter 'root'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
got rid of compilation warning:
ISO C90 forbids mixed declarations and code
Signed-off-by: Cordelia Sam <cordesam@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Not used anywhere yet, but this complements the existing plain
'insert_resource()' functionality with a version that can expand the
resource we are adding in order to fix up any conflicts it has with
existing resources.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pulling the ethernet cable on a 2.6.27-rc system with NFS mounts
currently leads to an ongoing flood of soft lockup detector backtraces
for all tasks blocked on the NFS mounts when the hickup takes
longer than 120s.
I don't think NFS problems should be all that noisy.
Luckily there's a reasonably easy way to distingush this case.
Don't report task softlockup warnings for tasks in TASK_KILLABLE
state, which is used by the network file systems.
I believe this patch is a 2.6.27 candidate.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In accordance with commit f42ac38c59
("ftrace: disable tracing for suspend to ram"), disable tracing
around the suspend code in hibernation code paths.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It fixes an accounting bug where we would continue accumulating runtime
even though the bandwidth control is disabled. This would lead to very long
throttle periods once bandwidth control gets turned on again.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix:
kernel/sched.c: In function '__rt_schedulable':
kernel/sched.c:8771: error: implicit declaration of function 'walk_tg_tree'
kernel/sched.c:8771: error: 'tg_nop' undeclared (first use in this function)
kernel/sched.c:8771: error: (Each undeclared identifier is reported only once
kernel/sched.c:8771: error: for each function it appears in.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
- During wake up of a new task, task_new_fair() can do a resched_task()
on the current task. Later in the code path, check_preempt_curr() also ends
up doing the same, which can be avoided. Check if TIF_NEED_RESCHED is
already set for the current task.
- task_new_fair() does a resched_task() on the current task unconditionally.
This can be done only in case when child runs before the parent.
So this is a small speedup.
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When sysctl_sched_rt_runtime is set to something other than -1 and the
CONFIG_RT_GROUP_SCHED kernel parameter is NOT enabled, we get into a state
where we see one or more CPUs idling forvever even though there are
real-time
tasks in their rt runqueue that are able to run (no longer throttled).
The sequence is:
- A real-time task is running when the timer sets the rt runqueue
to throttled, and the rt task is resched_task()ed and switched
out, and idle is switched in since there are no non-rt tasks to
run on that cpu.
- Eventually the do_sched_rt_period_timer() runs and un-throttles
the rt runqueue, but we just exit the timer interrupt and go back
to executing the idle task in the idle loop forever.
If we change the sched_rt_rq_enqueue() routine to use some of the code
from the CONFIG_RT_GROUP_SCHED enabled version of this same routine and
resched_task() the currently executing task (idle in our case) if it is
a lower priority task than the higher rt task in the now un-throttled
runqueue, the problem is no longer observed.
Signed-off-by: John Blackwood <john.blackwood@ccur.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I've been painstakingly debugging the issue with suspend to ram and
ftraced. The 2.6.28 code does not have this issue, but since the mcount
recording is not going to be in 27, this must be solved for the ftrace
daemon version.
The resume from suspend to ram would reboot because it was triple
faulting. Debugging further, I found that calling the mcount function
itself was not an issue, but it would fault when it incremented
preempt_count. preempt_count is on the tasks info structure that is on the
low memory address of the task's stack. For some reason, it could not
write to it. Resuming out of suspend to ram does quite a lot of funny
tricks to get to work, so it is not surprising at all that simply doing a
preempt_disable() would cause a fault.
Thanks to Rafael for suggesting to add a "while (1);" to find the place in
resuming that is causing the fault. I would place the loop somewhere in
the code, compile and reboot and see if it would either reboot (hit the
fault) or simply hang (hit the loop). Doing this over and over again, I
narrowed it down that it was happening in enable_nonboot_cpus.
At this point, I found that it is easier to simply disable tracing around
the suspend code, instead of searching for the particular function that
can not handle doing a preempt_disable.
This patch disables the tracer as it suspends and reenables it on resume.
I tested this patch on my Laptop, and it can resume fine with the patch.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CC kernel/rcuclassic.o
kernel/rcuclassic.c: In function 'rcu_init_percpu_data':
kernel/rcuclassic.c:705: warning: comparison of distinct pointer types lacks a cast
kernel/rcuclassic.c:713: warning: comparison of distinct pointer types lacks a cast
flags should be unsigned long.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
task->signal->notify_count is only initialized if
task->signal->group_exit_task is not NULL. Reorder a conditional so
that uninitialised memory is not used. Found by Valgrind.
Signed-off-by: Steve VanDeBogart <vandebo-lkml@nerdbox.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix bad contention counting in /proc/lock_stat.
/proc/lockstat tries to gather per-ip contention
statistics per-lock. This was failing due to
a garbage per-ip index selector being used.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix rounding error in /proc/lock_stat numerical output.
On occasion the two digit fractional part contains the three
digit value '100'. This is due to a bug in the rounding algorithm
which pushes values in the range '95..99' to '100' rather than
to '00' + an increment to the integer part. For example,
- 123456.100 old display
+ 123457.00 new display
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds kernel doc for the completion feature.
An error in the split-man.pl PERL snippet in kernel-doc-nano-HOWTO.txt is
also fixed.
Signed-off-by: Kevin Diggs <kevdig@hypersurf.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Have smp_call_function_single() return invalid CPU indicies and return
-ENXIO. This function is already executed inside a
get_cpu()..put_cpu() which locks out CPU removal, so rather than
having the higher layers doing another layer of locking to guard
against unplugged CPUs do the test here.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
'load_module()' is a complex function that contains all the ELF section
logic, and inlining it is utterly insane. But gcc will do it, simply
because there is only one call-site. As a result, all the stack space
that is allocated for all the work to load the module will still be
active when we actually call the module init sequence, and the deep call
chain makes stack overflows happen.
And stack overflows are really hard to debug, because they not only
corrupt random pages below the stack, but also corrupt the thread_info
structure that is allocated under the stack.
In this case, Alan Brunelle reported some crazy oopses at bootup, after
loading the processor module that ends up doing complex ACPI stuff and
has quite a deep callchain. This should fix it, and is the sane thing
to do regardless.
Cc: Alan D. Brunelle <Alan.Brunelle@hp.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch lets the files using linux/version.h match the files that
#include it.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
wait_task_inactive() returns 1 when p->nvcsw == 0 || p->nvcsw == 1. This
means that two subsequent calls can return the same number while the task
was scheduled in between.
Change the code to return "nvcsw | LONG_MIN" instead of "nvcsw ?: 1", now
the overlap always needs LONG_MAX schedules.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If wait_task_inactive() returns success the task was deactivated. In that
case schedule() always increments ->nvcsw which alone can be used as a
"generation counter".
If the next call returns the same number, we can be sure that the task was
unscheduled. Otherwise, because we know that .on_rq == 0 again, ->nvcsw
should have been changed in between.
Q: perhaps it is better to do "ncsw = (p->nvcsw << 1) | 1" ? This
decreases the possibility of "was it unscheduled" false positive when
->nvcsw == 0.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change do_wait_for_common() to use signal_pending_state() instead of open
coding.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When DEBUG_SHIRQ is selected, a spurious IRQ is issued before
the setup_irq() initializes the desc->depth. An IRQ handler may
call disable_irq_nosync(), but then setup_irq() will overwrite
desc->depth, and upon enable_irq() we'll catch this WARN:
------------[ cut here ]------------
Badness at kernel/irq/manage.c:180
NIP: c0061ab8 LR: c0061f10 CTR: 00000000
REGS: cf83be50 TRAP: 0700 Not tainted (2.6.27-rc3-23450-g74919b0)
MSR: 00021032 <ME,IR,DR> CR: 22042022 XER: 20000000
TASK = cf829100[5] 'events/0' THREAD: cf83a000
GPR00: c0061f10 cf83bf00 cf829100 c038e674 00000016 00000000 cf83bef8 00000038
GPR08: c0298910 00000000 c0310d28 cf83a000 00000c9c 1001a1a8 0fffe000 00800000
GPR16: ffffffff 00000000 007fff00 00000000 007ffeb0 c03320a0 c031095c c0310924
GPR24: cf8292ec cf807190 cf83a000 00009032 c038e6a4 c038e674 cf99b1cc c038e674
NIP [c0061ab8] __enable_irq+0x20/0x80
LR [c0061f10] enable_irq+0x50/0x70
Call Trace:
[cf83bf00] [c038e674] irq_desc+0x630/0x9000 (unreliable)
[cf83bf10] [c0061f10] enable_irq+0x50/0x70
[cf83bf30] [c01abe94] phy_change+0x68/0x108
[cf83bf50] [c0046394] run_workqueue+0xc4/0x16c
[cf83bf90] [c0046834] worker_thread+0x74/0xd4
[cf83bfd0] [c004ab7c] kthread+0x48/0x84
[cf83bff0] [c00135e0] kernel_thread+0x44/0x60
Instruction dump:
4e800020 3d20c031 38a94214 4bffffcc 9421fff0 7c0802a6 93e1000c 7c7f1b78
90010014 8123001c 2f890000 409e001c <0fe00000> 80010014 83e1000c 38210010
That trace corresponds to this line:
WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
The patch fixes the problem by moving the SHIRQ code below the
setup_irq().
Unfortunately we can't easily move the SHIRQ code inside the
setup_irq(), since it grabs a spinlock, so to prvent a 'real'
IRQ from interfere us we should disable that IRQ.
p.s. The driver in question is drivers/net/phy/phy.c.
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Thanks to the review by Michael Kerrisk a bug in the recent
ADJ_OFFSET_SS_READ option was discovered, where the ntp time_offset was
inadvertently set by it. This fixes this by making the adjtime code
more separate from the ntp_adjtime code (both of which really want to
be separate syscalls).
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some earlier tip/core/rcu patches caused RCU to incorrectly enable irqs
too early in boot. This caused Yinghai's repeated-kexec testing to
hit oopses, presumably due to so that device interrupts left over from
the prior kernel instance (which would oops the newly booting kernel
before it got a chance to reset said devices). This patch therefore
converts all the local_irq_disable()s in rcuclassic.c to local_irq_save().
Besides, I never did like local_irq_disable() anyway. ;-)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add the comment to explain why the double lock in migrate_timers()
can't deadlock.
Change the code to use spinlock_irq() instead of local_irq_disable()
+ spin_lock().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On the tickless system(CONFIG_NO_HZ=y and CONFIG_HIGH_RES_TIMERS=n), after
I made an offlined cpu online, I found this cpu's event handler was
tick_handle_periodic, not tick_nohz_handler.
After debuging, I found this bug was caused by the wrong tick mode. the
tick mode is not changed to NOHZ_MODE_INACTIVE when the cpu is offline.
This patch fixes this bug.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In talking with Josip Loncaric, and his work on clock synchronization (see
btime.sf.net), he mentioned that for really close synchronization, it is
useful to have access to "hardware time", that is a notion of time that is
not in any way adjusted by the clock slewing done to keep close time sync.
Part of the issue is if we are using the kernel's ntp adjusted
representation of time in order to measure how we should correct time, we
can run into what Paul McKenney aptly described as "Painting a road using
the lines we're painting as the guide".
I had been thinking of a similar problem, and was trying to come up with a
way to give users access to a purely hardware based time representation
that avoided users having to know the underlying frequency and mask values
needed to deal with the wide variety of possible underlying hardware
counters.
My solution is to introduce CLOCK_MONOTONIC_RAW. This exposes a
nanosecond based time value, that increments starting at bootup and has no
frequency adjustments made to it what so ever.
The time is accessed from userspace via the posix_clock_gettime() syscall,
passing CLOCK_MONOTONIC_RAW as the clock_id.
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
To keep the raw monotonic patch simple first introduce
clocksource_forward_now(), which takes care of the offset since the last
update_wall_time() call and adds it to the clock, so there is no need
anymore to deal with it explicitly at various places, which need to make
significant changes to the clock.
This is also gets rid of the timekeeping_suspend_nsecs, instead of
waiting until resume, the value is accumulated during suspend. In the end
there is only a single user of __get_nsec_offset() left, so I integrated
it back to getnstimeofday().
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The clocksource frequency is represented by
clocksource->mult/2^(clocksource->shift). Currently, when NTP makes
adjustments to the clock frequency, they are made directly to the mult
value.
This has the drawback that once changed, we cannot know what the orignal
mult value was, or how much adjustment has been applied.
This property causes problems in calculating proper ntp intervals when
switching back and forth between clocksources.
This patch separates the current mult value into a mult and mult_orig
pair. The mult_orig value stays constant, while the ntp clocksource
adjustments are done only to the mult value.
This allows for correct ntp interval calculation and additionally lays the
groundwork for a new notion of time, what I'm calling the monotonic-raw
time, which is introduced in a following patch.
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix RCU's synchronize_rcu() so that it looks like a C function, enabling
it to be recognized as a function with kernel-doc annotation.
Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'synchronize_rcu'
Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'call_rcu'
[akpm@linux-foundation.org: fix comment]
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Yanmin reported a significant regression on his 16-core machine due to:
commit 93b75217df
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri Jun 27 13:41:33 2008 +0200
Flip back to the old behaviour.
Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When user calls sys_setpriority(PRIO_PGRP ...) on a NPTL style multi-LWP
process, only the task leader of the process is affected, all other
sibling LWP threads didn't receive the setting. The problem was that the
iterator used in sys_setpriority() only iteartes over one task for each
process, ignoring all other sibling thread.
Introduce a new macro do_each_pid_thread / while_each_pid_thread to walk
each thread of a process. Convert 4 call sites in {set/get}priority and
ioprio_{set/get}.
Signed-off-by: Ken Chen <kenchen@google.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the comment describing the possibility of printk() deadlocking on
runqueue lock.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I outwitted myself again in commit 2b2a1ff64a,
and broke the SA_NOCLDWAIT behavior so it leaks zombies. This fixes it.
Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Roland McGrath <roland@redhat.com>
The last patch allows sysctl_sched_rt_runtime to disable bandwidth accounting
for the group scheduler - however it doesn't deal with sched_setscheduler(),
which will keep tasks out of groups that have no assigned runtime.
If we relax this, we get into the situation where RT tasks can get into a group
when we disable bandwidth control, and then starve them by enabling it again.
Rework the schedulability code to check for this condition and fail to turn
on bandwidth control with -EBUSY when this situation is found.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Extract walk_tg_tree() and make it a little more generic so we can use it
in the schedulablity test.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
More extensive disable of bandwidth control. It allows sysctl_sched_rt_runtime
to disable full group bandwidth control.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It fixes an accounting bug where we would continue accumulating runtime
even though the bandwidth control is disabled. This would lead to very long
throttle periods once bandwidth control gets turned on again.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix:
CC kernel/rcuclassic.o
kernel/rcuclassic.c: In function '__rcu_process_callbacks':
kernel/rcuclassic.c:561: error: 'flags' undeclared (first use in this function)
kernel/rcuclassic.c:561: error: (Each undeclared identifier is reported only once
kernel/rcuclassic.c:561: error: for each function it appears in.)
Declare missing variable flags.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Given that the rcp->lock is now acquired from call_rcu(), which can be
invoked from irq-disable regions, all acquisitions need to disable irqs.
The following patch fixes this.
Although I don't have any reason to believe that this is the cause of
Yinghai's oops, it does need to be fixed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove the redundant definition of ACCESS_ONCE() from rcupreempt.c in
favor of the one in compiler.h. Also merge the comment header from
rcupreempt.c's definition into that in compiler.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since f82b217e35 lockdep can output spurious
warnings related to hwirqs due to hardirq_off shrinkage from int to bit-sized
flag. Guard it with double negation to fix the warning.
Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
lockdep: fix build if CONFIG_PROVE_LOCKING not defined
lockdep: use WARN() in kernel/lockdep.c
lockdep: spin_lock_nest_lock(), checkpatch fixes
lockdep: build fix
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: scale sysctl_sched_shares_ratelimit with nr_cpus
sched: fix rt-bandwidth hotplug race
sched: fix the race between walk_tg_tree and sched_create_group
If CONFIG_PROVE_LOCKING not defined, then no dependency information
is available.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
David reported that his Niagra spend a little too much time in
tg_shares_up(), which considering he has a large cpu count makes sense.
So scale the ratelimit value with the number of cpus like we do for
other controls as well.
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In the initialization of the RCU trace module, if
rcupreempt_debugfs_init() fails, we never free the the trace buffer.
This patch frees the trace buffer in case the debugfs fails.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
m68k fails to build with these functions inlined in completion.h. Move
them out of line into sched.c and export them to avoid this problem.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ftrace depends on some processor state that we destroyed during kexec and
restored by restore_processor_state(). So save_processor_state() and
restore_processor_state() are moved into machine_kexec() and ftrace is
restored after restore_processor_state().
Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rename KEXEC_CONTROL_CODE_SIZE to KEXEC_CONTROL_PAGE_SIZE, because control
page is used for not only code on some platform. For example in kexec
jump, it is used for data and stack too.
[akpm@linux-foundation.org: unbreak powerpc and arm, finish conversion]
Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/kexec.c: In function 'kernel_kexec':
kernel/kexec.c:1506: warning: value computed is not used
Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch simplifies the locking and memory-barrier usage in the Classic
RCU grace-period-detection mechanism, incorporating Lai Jiangshan's
feedback from the earlier version (http://lkml.org/lkml/2008/8/1/400
and http://lkml.org/lkml/2008/8/3/43). Passed 10 hours of
rcutorture concurrent with CPUs being put online and taken offline on
a 128-hardware-thread Power machine. My apologies to whoever in the
Eastern Hemisphere was planning to use this machine over the Western
Hemisphere night, but it was sitting idle and...
So this is ready for tip/core/rcu.
This patch is in preparation for moving to a hierarchical
algorithm to allow the very large SMP machines -- requested by some
people at OLS, and there seem to have been a few recent patches in the
4096-CPU direction as well. The general idea is to move to a much more
conservative concurrency design, then apply a hierarchy to reduce
contention on the global lock by a few orders of magnitude (larger
machines would see greater reductions). The reason for taking a
conservative approach is that this code isn't on any fast path.
Prototype in progress.
This patch is against the linux-tip git tree (tip/core/rcu). If you
wish to test this against 2.6.26, use the following set of patches:
http://www.rdrop.com/users/paulmck/patches/2.6.26-ljsimp-1.patchhttp://www.rdrop.com/users/paulmck/patches/2.6.26-ljsimpfix-3.patch
The first patch combines commits 5127bed588
and 3cac97cbb1 from Lai Jiangshan
<laijs@cn.fujitsu.com>, and the second patch contains my changes.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
One small change needed to keep from flooding the console when one
CPU notices that another is AWOL. Unless I am missing something subtle.
Otherwise the cleanups look good!
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When we hot-unplug a cpu and rebuild the sched-domain, all cpus will be
detatched. Alex observed the case where a runqueue was stealing bandwidth
from an already disabled runqueue to satisfy its own needs.
Stop this by skipping over already disabled runqueues.
Reported-by: Alex Nixon <alex.nixon@citrix.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Alex Nixon <alex.nixon@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags
the target process if that is not the current process and it is trying to
change its own flags in a different way at the same time.
__capable() is using neither atomic ops nor locking to protect t->flags. This
patch removes __capable() and introduces has_capability() that doesn't set
PF_SUPERPRIV on the process being queried.
This patch further splits security_ptrace() in two:
(1) security_ptrace_may_access(). This passes judgement on whether one
process may access another only (PTRACE_MODE_ATTACH for ptrace() and
PTRACE_MODE_READ for /proc), and takes a pointer to the child process.
current is the parent.
(2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only,
and takes only a pointer to the parent process. current is the child.
In Smack and commoncap, this uses has_capability() to determine whether
the parent will be permitted to use PTRACE_ATTACH if normal checks fail.
This does not set PF_SUPERPRIV.
Two of the instances of __capable() actually only act on current, and so have
been changed to calls to capable().
Of the places that were using __capable():
(1) The OOM killer calls __capable() thrice when weighing the killability of a
process. All of these now use has_capability().
(2) cap_ptrace() and smack_ptrace() were using __capable() to check to see
whether the parent was allowed to trace any process. As mentioned above,
these have been split. For PTRACE_ATTACH and /proc, capable() is now
used, and for PTRACE_TRACEME, has_capability() is used.
(3) cap_safe_nice() only ever saw current, so now uses capable().
(4) smack_setprocattr() rejected accesses to tasks other than current just
after calling __capable(), so the order of these two tests have been
switched and capable() is used instead.
(5) In smack_file_send_sigiotask(), we need to allow privileged processes to
receive SIGIO on files they're manipulating.
(6) In smack_task_wait(), we let a process wait for a privileged process,
whether or not the process doing the waiting is privileged.
I've tested this with the LTP SELinux and syscalls testscripts.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
This is an updated version of my previous cpuset patch on top of
the latest mainline git.
The patch fixes CPU hotplug handling issues in the current cpusets code.
Namely circular locking in rebuild_sched_domains() and unsafe access to
the cpu_online_map in the cpuset cpu hotplug handler.
This version includes changes suggested by Paul Jackson (naming, comments,
style, etc). I also got rid of the separate workqueue thread because it is
now safe to call get_online_cpus() from workqueue callbacks.
Here are some more details:
rebuild_sched_domains() is the only way to rebuild sched domains
correctly based on the current cpuset settings. What this means
is that we need to be able to call it from different contexts,
like cpu hotplug for example.
Also latest scheduler code in -tip now calls rebuild_sched_domains()
directly from functions like arch_reinit_sched_domains().
In order to support that properly we need to rework cpuset locking
rules to avoid circular dependencies, which is what this patch does.
New lock nesting rules are explained in the comments.
We can now safely call rebuild_sched_domains() from virtually any
context. The only requirement is that it needs to be called under
get_online_cpus(). This allows cpu hotplug handlers and the scheduler
to call rebuild_sched_domains() directly.
The rest of the cpuset code now offloads sched domains rebuilds to
a workqueue (async_rebuild_sched_domains()).
This version of the patch addresses comments from the previous review.
I fixed all miss-formated comments and trailing spaces.
I also factored out the code that builds domain masks and split up CPU and
memory hotplug handling. This was needed to simplify locking, to avoid unsafe
access to the cpu_online_map from mem hotplug handler, and in general to make
things cleaner.
The patch passes moderate testing (building kernel with -j 16, creating &
removing domains and bringing cpus off/online at the same time) on the
quad-core2 based machine.
It passes lockdep checks, even with preemptable RCU enabled.
This time I also tested in with suspend/resume path and everything is working
as expected.
Signed-off-by: Max Krasnyansky <maxk@qualcomm.com>
Acked-by: Paul Jackson <pj@sgi.com>
Cc: menage@google.com
Cc: a.p.zijlstra@chello.nl
Cc: vegard.nossum@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Use WARN() instead of a printk+WARN_ON() pair; this way the message
becomes part of the warning section for better reporting/collection.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
fix:
kernel/built-in.o: In function `lockdep_stats_show':
lockdep_proc.c:(.text+0x3cb2f): undefined reference to `lockdep_count_forward_deps'
kernel/built-in.o: In function `l_show':
lockdep_proc.c:(.text+0x3d02b): undefined reference to `lockdep_count_forward_deps'
lockdep_proc.c:(.text+0x3d047): undefined reference to `lockdep_count_backward_deps'
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Switch /proc/irq/*/smp_affinity , /proc/irq/default_smp_affinity to
seq_files.
cat(1) reads with 1024 chunks by default, with high enough NR_CPUS, there
will be -EINVAL.
As side effect, there are now two less users of the ->read_proc interface.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
s390 doesn't support the additional_cpus kernel parameter anymore since a
long time. So we better update the code and documentation to reflect
that.
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'core-fixes-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
generic-ipi: fix stack and rcu interaction bug in smp_call_function_mask(), fix
* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
fix spinlock recursion in hvc_console
stop_machine: remove unused variable
modules: extend initcall_debug functionality to the module loader
export virtio_rng.h
lguest: use get_user_pages_fast() instead of get_user_pages()
mm: Make generic weak get_user_pages_fast and EXPORT_GPL it
lguest: don't set MAC address for guest unless specified
> > Nick Piggin (1):
> > generic-ipi: fix stack and rcu interaction bug in
> > smp_call_function_mask()
>
> I'm still not 100% sure that I have this patch right... I might have seen
> a lockup trace implicating the smp call function path... which may have
> been due to some other problem or a different bug in the new call function
> code, but if some more people can take a look at it before merging?
OK indeed it did have a couple of bugs. Firstly, I wasn't freeing the
data properly in the alloc && wait case. Secondly, I wasn't resetting
CSD_FLAG_WAIT in the for each cpu loop (so only the first CPU would
wait).
After those fixes, the patch boots and runs with the kmalloc commented
out (so it always executes the slowpath).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The kernel has this really nice facility where if you put "initcall_debug"
on the kernel commandline, it'll print which function it's going to
execute just before calling an initcall, and then after the call completes
it will
1) print if it had an error code
2) checks for a few simple bugs (like leaving irqs off)
and
3) print how long the init call took in milliseconds.
While trying to optimize the boot speed of my laptop, I have been loving
number 3 to figure out what to optimize... ... and then I wished that
the same thing was done for module loading.
This patch makes the module loader use this exact same functionality; it's
a logical extension in my view (since modules are just sort of late
binding initcalls anyway) and so far I've found it quite useful in finding
where things are too slow in my boot.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched, cpu hotplug: fix set_cpus_allowed() use in hotplug callbacks
sched: fix mysql+oltp regression
sched_clock: delay using sched_clock()
sched clock: couple local and remote clocks
sched clock: simplify __update_sched_clock()
sched: eliminate scd->prev_raw
sched clock: clean up sched_clock_cpu()
sched clock: revert various sched_clock() changes
sched: move sched_clock before first use
sched: test runtime rather than period in global_rt_runtime()
sched: fix SCHED_HRTICK dependency
sched: fix warning in hrtick_start_fair()
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
posix-timers: fix posix_timer_event() vs dequeue_signal() race
posix-timers: do_schedule_next_timer: fix the setting of ->si_overrun
When we enable DEBUG_LOCK_ALLOC but do not enable PROVE_LOCKING and or
LOCK_STAT, lock_alloc() and lock_release() turn into nops, even though
we should be doing hlock checking (check=1).
This causes a false warning and a lockdep self-disable.
Rectify this.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Mark Langsdorf reported:
> One of my co-workers noticed that the powernow-k8
> driver no longer restarts when a CPU core is
> hot-disabled and then hot-enabled on AMD quad-core
> systems.
>
> The following comands work fine on 2.6.26 and fail
> on 2.6.27-rc1:
>
> echo 0 > /sys/devices/system/cpu/cpu3/online
> echo 1 > /sys/devices/system/cpu/cpu3/online
> find /sys -name cpufreq
>
> For 2.6.26, the find will return a cpufreq
> directory for each processor. In 2.6.27-rc1,
> the cpu3 directory is missing.
>
> After digging through the code, the following
> logic is failing when the core is hot-enabled
> at runtime. The code works during the boot
> sequence.
>
> cpumask_t = current->cpus_allowed;
> set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
> if (smp_processor_id() != cpu)
> return -ENODEV;
So set the CPU active before calling the CPU_ONLINE notifier chain,
there are a handful of notifiers that use set_cpus_allowed().
This fix also solves the problem with x86-microcode. I've sent
alternative patches for microcode, but as this "rely on
set_cpus_allowed_ptr() being workable in cpu-hotplug(CPU_ONLINE, ...)"
assumption seems to be more broad than what we thought, perhaps this fix
should be applied.
With this patch we define that by the moment CPU_ONLINE is being sent,
a 'cpu' is online and ready for tasks to be migrated onto it.
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Reported-by: Mark Langsdorf <mark.langsdorf@amd.com>
Tested-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Venki Pallipadi <venkatesh.pallipadi@intel.com> wrote:
> Found a OOPS on a big SMP box during an overnight reboot test with
> upstream git.
>
> Suresh and I looked at the oops and looks like the root cause is in
> generic_smp_call_function_interrupt() and smp_call_function_mask() with
> wait parameter.
>
> The actual oops looked like
>
> [ 11.277260] BUG: unable to handle kernel paging request at ffff8802ffffffff
> [ 11.277815] IP: [<ffff8802ffffffff>] 0xffff8802ffffffff
> [ 11.278155] PGD 202063 PUD 0
> [ 11.278576] Oops: 0010 [1] SMP
> [ 11.279006] CPU 5
> [ 11.279336] Modules linked in:
> [ 11.279752] Pid: 0, comm: swapper Not tainted 2.6.27-rc2-00020-g685d87f #290
> [ 11.280039] RIP: 0010:[<ffff8802ffffffff>] [<ffff8802ffffffff>] 0xffff8802ffffffff
> [ 11.280692] RSP: 0018:ffff88027f1f7f70 EFLAGS: 00010086
> [ 11.280976] RAX: 00000000ffffffff RBX: 0000000000000000 RCX: 0000000000000000
> [ 11.281264] RDX: 0000000000004f4e RSI: 0000000000000001 RDI: 0000000000000000
> [ 11.281624] RBP: ffff88027f1f7f98 R08: 0000000000000001 R09: ffffffff802509af
> [ 11.281925] R10: ffff8800280c2780 R11: 0000000000000000 R12: ffff88027f097d48
> [ 11.282214] R13: ffff88027f097d70 R14: 0000000000000005 R15: ffff88027e571000
> [ 11.282502] FS: 0000000000000000(0000) GS:ffff88027f1c3340(0000) knlGS:0000000000000000
> [ 11.283096] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> [ 11.283382] CR2: ffff8802ffffffff CR3: 0000000000201000 CR4: 00000000000006e0
> [ 11.283760] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 11.284048] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 11.284337] Process swapper (pid: 0, threadinfo ffff88027f1f2000, task ffff88027f1f0640)
> [ 11.284936] Stack: ffffffff80250963 0000000000000212 0000000000ee8c78 0000000000ee8a66
> [ 11.285802] ffff88027e571550 ffff88027f1f7fa8 ffffffff8021adb5 ffff88027f1f3e40
> [ 11.286599] ffffffff8020bdd6 ffff88027f1f3e40 <EOI> ffff88027f1f3ef8 0000000000000000
> [ 11.287120] Call Trace:
> [ 11.287768] <IRQ> [<ffffffff80250963>] ? generic_smp_call_function_interrupt+0x61/0x12c
> [ 11.288354] [<ffffffff8021adb5>] smp_call_function_interrupt+0x17/0x27
> [ 11.288744] [<ffffffff8020bdd6>] call_function_interrupt+0x66/0x70
> [ 11.289030] <EOI> [<ffffffff8024ab3b>] ? clockevents_notify+0x19/0x73
> [ 11.289380] [<ffffffff803b9b75>] ? acpi_idle_enter_simple+0x18b/0x1fa
> [ 11.289760] [<ffffffff803b9b6b>] ? acpi_idle_enter_simple+0x181/0x1fa
> [ 11.290051] [<ffffffff8053aeca>] ? cpuidle_idle_call+0x70/0xa2
> [ 11.290338] [<ffffffff80209f61>] ? cpu_idle+0x5f/0x7d
> [ 11.290723] [<ffffffff8060224a>] ? start_secondary+0x14d/0x152
> [ 11.291010]
> [ 11.291287]
> [ 11.291654] Code: Bad RIP value.
> [ 11.292041] RIP [<ffff8802ffffffff>] 0xffff8802ffffffff
> [ 11.292380] RSP <ffff88027f1f7f70>
> [ 11.292741] CR2: ffff8802ffffffff
> [ 11.310951] ---[ end trace 137c54d525305f1c ]---
>
> The problem is with the following sequence of events:
>
> - CPU A calls smp_call_function_mask() for CPU B with wait parameter
> - CPU A sets up the call_function_data on the stack and does an rcu add to
> call_function_queue
> - CPU A waits until the WAIT flag is cleared
> - CPU B gets the call function interrupt and starts going through the
> call_function_queue
> - CPU C also gets some other call function interrupt and starts going through
> the call_function_queue
> - CPU C, which is also going through the call_function_queue, starts referencing
> CPU A's stack, as that element is still in call_function_queue
> - CPU B finishes the function call that CPU A set up and as there are no other
> references to it, rcu deletes the call_function_data (which was from CPU A
> stack)
> - CPU B sees the wait flag and just clears the flag (no call_rcu to free)
> - CPU A which was waiting on the flag continues executing and the stack
> contents change
>
> - CPU C is still in rcu_read section accessing the CPU A's stack sees
> inconsistent call_funation_data and can try to execute
> function with some random pointer, causing stack corruption for A
> (by clearing the bits in mask field) and oops.
Nice debugging work.
I'd suggest something like the attached (boot tested) patch as the simple
fix for now.
I expect the benefits from the less synchronized, multiple-in-flight-data
global queue will still outweigh the costs of dynamic allocations. But
if worst comes to worst then we just go back to a globally synchronous
one-at-a-time implementation, but that would be pretty sad!
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Defer commit 6d299f1b53 to the next release.
Testing of the tip/sched/clock tree revealed a mysql+oltp regression
which bisection eventually traced back to this commit in mainline.
Pertinent test results: Three run sysbench averages, throughput units
in read/write requests/sec.
clients 1 2 4 8 16 32 64
6e0534f 9646 17876 34774 33868 32230 30767 29441
2.6.26.1 9112 17936 34652 33383 31929 30665 29232
6d299f1 9112 14637 28370 33339 32038 30762 29204
Note: subsequent commits hide the majority of this regression until you
apply the clock fixes, at which time it reemerges at full magnitude.
We cannot see anything bad about the change itself so we defer it to the
next release until this problem is fully analysed.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Avoid deadlocks against rq->lock and xtime_lock by deferring the klogd
wakeup by polling from the timer tick.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
this is a diagnostic patch for Classic RCU.
The approach is to record a timestamp at the beginning
of the grace period (in rcu_start_batch()), then have
rcu_check_callbacks() complain if:
1. it is running on a CPU that has holding up grace periods for
a long time (say one second). This will identify the culprit
assuming that the culprit has not disabled hardware irqs,
instruction execution, or some such.
2. it is running on a CPU that is not holding up grace periods,
but grace periods have been held up for an even longer time
(say two seconds).
It is enabled via the default-off CONFIG_DEBUG_RCU_STALL kernel parameter.
Rather than exponential backoff, it backs off to once per 30 seconds.
My feeling upon thinking on it was that if you have stalled RCU grace
periods for that long, a few extra printk() messages are probably the
least of your worries...
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: David Witbrodt <dawitbro@sbcglobal.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
the names were too generic:
drivers/uio/uio.c:87: error: expected identifier or '(' before 'do'
drivers/uio/uio.c:87: error: expected identifier or '(' before 'while'
drivers/uio/uio.c:113: error: 'map_release' undeclared here (not in a function)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Solve this by marking the classes as unused and not printing information
about the unused classes.
Reported-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Acked-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Expose the new lock protection lock.
This can be used to annotate places where we take multiple locks of the
same class and avoid deadlocks by always taking another (top-level) lock
first.
NOTE: we're still bound to the MAX_LOCK_DEPTH (48) limit.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On Fri, 2008-08-01 at 16:26 -0700, Linus Torvalds wrote:
> On Fri, 1 Aug 2008, David Miller wrote:
> >
> > Taking more than a few locks of the same class at once is bad
> > news and it's better to find an alternative method.
>
> It's not always wrong.
>
> If you can guarantee that anybody that takes more than one lock of a
> particular class will always take a single top-level lock _first_, then
> that's all good. You can obviously screw up and take the same lock _twice_
> (which will deadlock), but at least you cannot get into ABBA situations.
>
> So maybe the right thing to do is to just teach lockdep about "lock
> protection locks". That would have solved the multi-queue issues for
> networking too - all the actual network drivers would still have taken
> just their single queue lock, but the one case that needs to take all of
> them would have taken a separate top-level lock first.
>
> Never mind that the multi-queue locks were always taken in the same order:
> it's never wrong to just have some top-level serialization, and anybody
> who needs to take <n> locks might as well do <n+1>, because they sure as
> hell aren't going to be on _any_ fastpaths.
>
> So the simplest solution really sounds like just teaching lockdep about
> that one special case. It's not "nesting" exactly, although it's obviously
> related to it.
Do as Linus suggested. The lock protection lock is called nest_lock.
Note that we still have the MAX_LOCK_DEPTH (48) limit to consider, so anything
that spills that it still up shit creek.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Most the free-standing lock_acquire() usages look remarkably similar, sweep
them into a new helper.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Instead of using a per-rq lock class, use the regular nesting operations.
However, take extra care with double_lock_balance() as it can release the
already held rq->lock (and therefore change its nesting class).
So what can happen is:
spin_lock(rq->lock); // this rq subclass 0
double_lock_balance(rq, other_rq);
// release rq
// acquire other_rq->lock subclass 0
// acquire rq->lock subclass 1
spin_unlock(other_rq->lock);
leaving you with rq->lock in subclass 1
So a subsequent double_lock_balance() call can try to nest a subclass 1
lock while already holding a subclass 1 lock.
Fix this by introducing double_unlock_balance() which releases the other
rq's lock, but also re-sets the subclass for this rq's lock to 0.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
this can be used to reset a held lock's subclass, for arbitrary-depth
iterated data structures such as trees or lists which have per-node
locks.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some arch's can't handle sched_clock() being called too early - delay
this until sched_clock_init() has been called.
Reported-by: Bill Gatliff <bgat@billgatliff.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Nishanth Aravamudan <nacc@us.ibm.com>
CC: Russell King - ARM Linux <linux@arm.linux.org.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
A documentation cleanup patch. With a minor tweak to clarify units for
kbs.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: mark gross <mgross@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
get_order() takes byte-sized input, not a page-granular one.
Irrespective of this fix I'm inclined to believe that this doesn't work
right anyway - bitmap_allocate_region() has an implicit assumption of
'pos' being suitable for 'order', which this function doesn't seem to
enforce (and since it's being called with a byte-granular value there's no
reason to believe that the callers would make sure device_addr is passed
accordingly - it's also not documented that way).
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Dmitry Baryshkov <dbaryshkov@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While I'm glad to finally see the hole fixed whereby passing an invalid
IRQ trigger type to request_irq() would be ignored, the current diagnostic
isn't quite useful. Fixed by also listing the trigger type which was
rejected.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change __down_common() to use signal_pending_state() instead of open
coding.
The changes in kernel/semaphore.o are just artifacts, the state checks are
optimized away.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In relay's current read implementation, if the buffer is completely full
but hasn't triggered the buffer-full condition (i.e. the last write
didn't cross the subbuffer boundary) and the last subbuffer is exactly
full, the subbuffer accounting code erroneously finds nothing available.
This patch fixes the problem.
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Andrea Righi <righi.andrea@gmail.com>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'audit.b56' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current:
Re: [PATCH] Fix the kernel panic of audit_filter_task when key field is set
The "user" parameter to __sched_setscheduler indicates whether the
change is being done on behalf of a user process or not. If not, we
shouldn't apply any permissions checks, so don't call
security_task_setscheduler().
Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Sorry, I miss a blank between if and "(".
And I add "unlikely" to check "ctx" in audit_match_perm() and audit_match_filetype().
This is a new patch for it.
Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
My commit 2b2a1ff64a introduced a regression
(sorry about that) for the odd case of exit_signal=0 (e.g. clone_flags=0).
This is not a normal use, but it's used by a case in the glibc test suite.
Dying with exit_signal=0 sends no signal, but it's supposed to wake up a
parent's blocked wait*() calls (unlike the delayed_group_leader case).
This fixes tracehook_notify_death() and its caller to distinguish a
"signal 0" wakeup from the delayed_group_leader case (with no wakeup).
Signed-off-by: Roland McGrath <roland@redhat.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb:
kgdb: fix gdb serial thread queries
kgdb: fix kgdb_validate_break_address to perform a mem write
kgdb: remove the requirement for CONFIG_FRAME_POINTER
When the "status_get->mask" is "AUDIT_STATUS_RATE_LIMIT || AUDIT_STATUS_BACKLOG_LIMIT".
If "audit_set_rate_limit" fails and "audit_set_backlog_limit" succeeds, the "err" value
will be greater than or equal to 0. It will miss the failure of rate set.
Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
When calling audit_filter_task(), it calls audit_filter_rules() with audit_context is NULL.
If the key field is set, the result in audit_filter_rules() will be set to 1 and
ctx->filterkey will be set to key.
But the ctx is NULL in this condition, so kernel will panic.
Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> shouldn't these be using the "audit_get_loginuid(current)" and if we
> are going to output loginuid we also should be outputting sessionid
Thanks for your detailed explanation.
I have made a new patch for outputing "loginuid" and "sessionid" by audit_get_loginuid(current) and audit_get_sessionid(current).
If there are some deficiencies, please give me your indication.
Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Hello,
According to my understanding there is an off-by-one bug in the
function:
audit_string_contains_control()
in:
kernel/audit.c
Patch is included.
I do not know from how many places the function is called from, but for
example, SELinux Access Vector Cache tries to log untrusted filenames via
call path:
avc_audit()
audit_log_untrustedstring()
audit_log_n_untrustedstring()
audit_string_contains_control()
If audit_string_contains_control() detects control characters, then the
string is hex-encoded. But the hex=0x7f dec=127, DEL-character, is not
detected.
I guess this could have at least some minor security implications, since a
user can create a filename with 0x7f in it, causing logged filename to
possibly look different when someone reads it on the terminal.
Signed-off-by: Vesa-Matti Kari <vmkari@cc.helsinki.fi>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Makes the kernel audit subsystem collect information about the sending
process when that process sends SIGUSR2 to the userspace audit daemon.
SIGUSR2 is a new interesting signal to auditd telling auditd that it
should try to start logging to disk again and the error condition which
caused it to stop logging to disk (usually out of space) has been
rectified.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The command "info threads" did not work correctly with kgdb. It would
result in a silent kernel hang if used.
This patach addresses several problems.
- Fix use of deprecated NR_CPUS
- Fix kgdb to not walk linearly through the pid space
- Correctly implement shadow pids
- Change the threads per query to a #define
- Fix kgdb_hex2long to work with negated values
The threads 0 and -1 are reserved to represent the current task. That
means that CPU 0 will start with a shadow thread id of -2, and CPU 1
will have a shadow thread id of -3, etc...
From the debugger you can switch to a shadow thread to see what one of
the other cpus was doing, however it is not possible to execute run
control operations on any other cpu execept the cpu executing the
kgdb_handle_exception().
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
A regression to the kgdb core was found in the case of using the
CONFIG_DEBUG_RODATA kernel option. When this option is on, a breakpoint
cannot be written into any readonly memory page. When an external
debugger requests a breakpoint to get set, the
kgdb_validate_break_address() was only checking to see if the address
to place the breakpoint was readable and lacked a write check.
This patch changes the validate routine to try reading (via the
breakpoint set request) and also to try immediately writing the break
point. If either fails, an error is correctly returned and the
debugger behaves correctly. Then an end user can make the
descision to use hardware breakpoints.
Also update the documentation to reflect that using
CONFIG_DEBUG_RODATA will inhibit the use of software breakpoints.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
While thinking about David's graph walk lockdep patch it _finally_
dawned on me that there is no reason we have a lock class per cpu ...
Sorry for being dense :-/
The below changes the annotation from a lock class per cpu, to a single
nested lock, as the scheduler never holds more that 2 rq locks at a time
anyway.
If there was code requiring holding all rq locks this would not work and
the original annotation would be the only option, but that not being the
case, this is a much lighter one.
Compiles and boots on a 2-way x86_64.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When we traverse the graph, either forwards or backwards, we
are interested in whether a certain property exists somewhere
in a node reachable in the graph.
Therefore it is never necessary to traverse through a node more
than once to get a correct answer to the given query.
Take advantage of this property using a global ID counter so that we
need not clear all the markers in all the lock_class entries before
doing a traversal. A new ID is choosen when we start to traverse, and
we continue through a lock_class only if it's ID hasn't been marked
with the new value yet.
This short-circuiting is essential especially for high CPU count
systems. The scheduler has a runqueue per cpu, and needs to take
two runqueue locks at a time, which leads to long chains of
backwards and forwards subgraphs from these runqueue lock nodes.
Without the short-circuit implemented here, a graph traversal on
a runqueue lock can take up to (1 << (N - 1)) checks on a system
with N cpus.
For anything more than 16 cpus or so, lockdep will eventually bring
the machine to a complete standstill.
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When taking the time of a remote CPU, use the opportunity to
couple (sync) the clocks to each other. (in a monotonic way)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
- return the current clock instead of letting callers
fetch it from scd->clock
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
