Impact: fix preemptoff and preemptirqsoff tracer self-tests
I was wondering why the preemptoff and preemptirqsoff tracer selftests
don't work on s390. After all its just that they get called from
non-preemptible context:
kernel_init() will execute all initcalls, however the first line in
kernel_init() is lock_kernel(), which causes the preempt_count to be
increased. Any later calls to add_preempt_count() (especially those
from the selftests) will therefore not result in a call to
trace_preempt_off() since the check below in add_preempt_count()
will be false:
if (preempt_count() == val)
trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
Hence the trace buffer will be empty.
Fix this by releasing the BKL during the self-tests.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: extend the ->init() method with the ability to fail
This bring a way to know if the initialization of a tracer successed.
A tracer must return 0 on success and a traditional error (ie:
-ENOMEM) if it fails.
If a tracer fails to init, it is free to print a detailed warn. The
tracing api will not and switch to a new tracer will just return the
error from the init callback.
Note: this will be used for the return tracer.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix confusing write() -EINVAL when changing the tracer
The following commit d9e540762f remade
alive the bug which made the set of a new tracer returning -EINVAL if
this is the longest name of tracer. This patch corrects it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: set filtered functions at time the filter is set
It can be confusing when the set_filter_functions is set (or cleared)
and the functions being recorded by the dynamic tracer does not
match.
This patch causes the code to be updated if the function tracer is
enabled and the filter is changed.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: correct implementation of dyn ftrace filter
The old decisions made by the filter algorithm was complex and incorrect.
This lead to inconsistent enabling or disabling of functions when
the filter was used.
This patch simplifies that code and in doing so, corrects the usage
of the filters.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: make ftrace_convert_nops() more permissive
Due to the way different architecture linkers combine the data sections
of the mcount_loc (the section that lists all the locations that
call mcount), there may be zeros added in that section. This is usually
due to strange alignments that the linker performs, that pads in zeros.
This patch makes the conversion code to nops skip any pointer in
the mcount_loc section that is NULL.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: allow archs more flexibility on dynamic ftrace implementations
Dynamic ftrace has largly been developed on x86. Since x86 does not
have the same limitations as other architectures, the ftrace interaction
between the generic code and the architecture specific code was not
flexible enough to handle some of the issues that other architectures
have.
Most notably, module trampolines. Due to the limited branch distance
that archs make in calling kernel core code from modules, the module
load code must create a trampoline to jump to what will make the
larger jump into core kernel code.
The problem arises when this happens to a call to mcount. Ftrace checks
all code before modifying it and makes sure the current code is what
it expects. Right now, there is not enough information to handle modifying
module trampolines.
This patch changes the API between generic dynamic ftrace code and
the arch dependent code. There is now two functions for modifying code:
ftrace_make_nop(mod, rec, addr) - convert the code at rec->ip into
a nop, where the original text is calling addr. (mod is the
module struct if called by module init)
ftrace_make_caller(rec, addr) - convert the code rec->ip that should
be a nop into a caller to addr.
The record "rec" now has a new field called "arch" where the architecture
can add any special attributes to each call site record.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix lockdep disabling itself when function tracing is enabled
The raw_local_irq_saves used in ftrace is causing problems with
lockdep. (it thinks the irq flags are out of sync and disables
itself with a warning)
The raw ops here are not needed, and the normal local_irq_save is fine.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: keep from converting freed records
When the tracer is started or stopped, it converts all code pointed
to by the saved records into callers to ftrace or nops. When modules
are unloaded, their records are freed, but they still exist within
the record pages.
This patch changes the code to skip over freed records.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: robust feature to disable ftrace on start or stop tracing on error
Currently only the initial conversion to nops will disable ftrace
on an anomaly. But if an anomaly happens on start or stopping of the
tracer, it will silently fail.
This patch adds a check there too, to disable ftrace and warn if the
conversion fails.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: let module functions be recorded when dyn ftrace not enabled
When dynamic ftrace had a daemon and a hash to record the locations
of mcount callers at run time, the recording needed to stop when
ftrace was disabled. But now that the recording is done at compile time
and the ftrace_record_ip is only called at boot up and when a module
is loaded, we no longer need to check if ftrace_enabled is set.
In fact, this breaks module load if it is not set because we skip
over module functions.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Because it has goto out before ftrace_list == &ftrace_list_end,
that's to say, we never meet this condition.
Signed-off-by: walimis <walimisdev@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Pekka reported a crash when resizing the mmiotrace tracer (if only
mmiotrace is enabled).
This happens because in that case we do not allocate the max buffer,
but we try to use it.
Make ring_buffer_resize() idempotent against NULL buffers.
Reported-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: better handling of CPU buffer start annotation
Because of the confusion with the per CPU buffers wrapping where
one CPU might be more active at the end of the trace than the other
CPUs causing that one CPU to have a shorter history. Kernel
developers were confused by the "missing" data of that one CPU
at the beginning of the trace output. An annotation was added to
the trace output to show that the buffer had started:
# tracer: function
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
##### CPU 3 buffer started ####
<idle>-0 [003] 158.192959: smp_apic_timer_interrupt
[...]
<idle>-0 [003] 161.556520: default_idle
##### CPU 1 buffer started ####
<idle>-0 [001] 161.592494: hrtimer_force_reprogram
[etc]
But this annotation gets a bit messy when tracers do not fill the
buffers. This patch does a couple of things:
One) it adds a flag to trace_options to disable these annotations
Two) it does not annotate if the tracer did not overflow its buffer.
This makes the output much cleaner.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: rename file /debug/tracing/iter_ctrl to /debug/tracing/trace_options
The original ftrace had a file called "iter_ctrl" that would control
the way the output was iterated. But this file grew into a catch all
for different trace options. This patch renames the file from iter_ctrl
to trace_options to reflect this change.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: change the units of buffer_size_kb to kilobytes
This patch changes the units of the buffer_size_kb file to kilobytes.
Reading and writing to the file uses kilobytes as units. To help
users to know what units are used, the output of the file now
looks like:
# cat /debug/tracing/buffer_size_kb
1408
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: rename of debugfs file trace_entries to buffer_size_kb
The original ftrace had fixed size entries, and the number of entries
was shown and modified via the file called trace_entries. By converting
to the unified trace buffer, we now allow for variable size entries
which makes the meaning of trace_entries pointless.
Since trace_size might be confused to the size of the trace, this patch
names it "buffer_size_kb" (thanks to Arjan van de Ven for this idea).
[ mingo@elte.hu: changed from buffer_size to buffer_size_kb ]
( Note, the units are still bytes - the next patch changes that,
to keep the wide rename patch separate from the unit-change patch. )
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: File name change of trace_unlikely.c
The "unlikely" name for the tracer is quite ugly. We renamed all the
parts of it to "branch" and now it is time to rename the file too.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: added new branch tracer
Currently the tracing of branch profiling (unlikelys and likelys hit)
is only activated by the iter_ctrl. This patch adds a tracer called
"branch" that will just trace the branch profiling. The advantage
of adding this tracer is that it can be added to the ftrace selftests
on startup.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: rename of iter_ctrl unlikely to branch
The unlikely name is ugly. This patch converts the iter_ctrl command
"unlikely" and "nounlikely" to "branch" and "nobranch" respectively.
It also renames a lot of internal functions to use "branch" instead
of "unlikely".
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: name change of unlikely tracer and profiler
Ingo Molnar suggested changing the config from UNLIKELY_PROFILE
to BRANCH_PROFILING. I never did like the "unlikely" name so I
went one step farther, and renamed all the unlikely configurations
to a "BRANCH" variant.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Steve suggested the to change the output from this:
> bash-3471 [003] 357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
> bash-3471 [003] 357.014756: [ .... ] update_curr:sched_fair.c:489
> bash-3471 [003] 357.014758: [ .... ] calc_delta_fair:sched_fair.c:411
to this:
> bash-3471 [003] 357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
> bash-3471 [003] 357.014756: [ ok ] update_curr:sched_fair.c:489
> bash-3471 [003] 357.014758: [ ok ] calc_delta_fair:sched_fair.c:411
as it makes it clearer to the user what it means exactly.
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: modify the tracer output, to make it a bit easier to read
Change the output from:
> bash-3471 [003] 357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
> bash-3471 [003] 357.014756: [correct] update_curr:sched_fair.c:489
> bash-3471 [003] 357.014758: [correct] calc_delta_fair:sched_fair.c:411
to:
> bash-3471 [003] 357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
> bash-3471 [003] 357.014756: [ .... ] update_curr:sched_fair.c:489
> bash-3471 [003] 357.014758: [ .... ] calc_delta_fair:sched_fair.c:411
it's good to have fields aligned vertically, and the only important
information is a prediction miss, so display only that information.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: new likely/unlikely branch tracer
This patch adds a way to record the instances of the likely() and unlikely()
branch condition annotations.
When "unlikely" is set in /debugfs/tracing/iter_ctrl the unlikely conditions
will be added to any of the ftrace tracers. The change takes effect when
a new tracer is passed into the current_tracer file.
For example:
bash-3471 [003] 357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
bash-3471 [003] 357.014756: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014758: [correct] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
bash-3471 [003] 357.014761: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014765: [correct] calc_delta_mine:sched.c:1279
Which shows the normal tracer heading, as well as whether the condition was
correct "[correct]" or was mistaken "[INCORRECT]", followed by the function,
file name and line number.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: new unlikely/likely profiler
Andrew Morton recently suggested having an in-kernel way to profile
likely and unlikely macros. This patch achieves that goal.
When configured, every(*) likely and unlikely macro gets a counter attached
to it. When the condition is hit, the hit and misses of that condition
are recorded. These numbers can later be retrieved by:
/debugfs/tracing/profile_likely - All likely markers
/debugfs/tracing/profile_unlikely - All unlikely markers.
# cat /debug/tracing/profile_unlikely | head
correct incorrect % Function File Line
------- --------- - -------- ---- ----
2167 0 0 do_arch_prctl process_64.c 832
0 0 0 do_arch_prctl process_64.c 804
2670 0 0 IS_ERR err.h 34
71230 5693 7 __switch_to process_64.c 673
76919 0 0 __switch_to process_64.c 639
43184 33743 43 __switch_to process_64.c 624
12740 64181 83 __switch_to process_64.c 594
12740 64174 83 __switch_to process_64.c 590
# cat /debug/tracing/profile_unlikely | \
awk '{ if ($3 > 25) print $0; }' |head -20
44963 35259 43 __switch_to process_64.c 624
12762 67454 84 __switch_to process_64.c 594
12762 67447 84 __switch_to process_64.c 590
1478 595 28 syscall_get_error syscall.h 51
0 2821 100 syscall_trace_leave ptrace.c 1567
0 1 100 native_smp_prepare_cpus smpboot.c 1237
86338 265881 75 calc_delta_fair sched_fair.c 408
210410 108540 34 calc_delta_mine sched.c 1267
0 54550 100 sched_info_queued sched_stats.h 222
51899 66435 56 pick_next_task_fair sched_fair.c 1422
6 10 62 yield_task_fair sched_fair.c 982
7325 2692 26 rt_policy sched.c 144
0 1270 100 pre_schedule_rt sched_rt.c 1261
1268 48073 97 pick_next_task_rt sched_rt.c 884
0 45181 100 sched_info_dequeued sched_stats.h 177
0 15 100 sched_move_task sched.c 8700
0 15 100 sched_move_task sched.c 8690
53167 33217 38 schedule sched.c 4457
0 80208 100 sched_info_switch sched_stats.h 270
30585 49631 61 context_switch sched.c 2619
# cat /debug/tracing/profile_likely | awk '{ if ($3 > 25) print $0; }'
39900 36577 47 pick_next_task sched.c 4397
20824 15233 42 switch_mm mmu_context_64.h 18
0 7 100 __cancel_work_timer workqueue.c 560
617 66484 99 clocksource_adjust timekeeping.c 456
0 346340 100 audit_syscall_exit auditsc.c 1570
38 347350 99 audit_get_context auditsc.c 732
0 345244 100 audit_syscall_entry auditsc.c 1541
38 1017 96 audit_free auditsc.c 1446
0 1090 100 audit_alloc auditsc.c 862
2618 1090 29 audit_alloc auditsc.c 858
0 6 100 move_masked_irq migration.c 9
1 198 99 probe_sched_wakeup trace_sched_switch.c 58
2 2 50 probe_wakeup trace_sched_wakeup.c 227
0 2 100 probe_wakeup_sched_switch trace_sched_wakeup.c 144
4514 2090 31 __grab_cache_page filemap.c 2149
12882 228786 94 mapping_unevictable pagemap.h 50
4 11 73 __flush_cpu_slab slub.c 1466
627757 330451 34 slab_free slub.c 1731
2959 61245 95 dentry_lru_del_init dcache.c 153
946 1217 56 load_elf_binary binfmt_elf.c 904
102 82 44 disk_put_part genhd.h 206
1 1 50 dst_gc_task dst.c 82
0 19 100 tcp_mss_split_point tcp_output.c 1126
As you can see by the above, there's a bit of work to do in rethinking
the use of some unlikelys and likelys. Note: the unlikely case had 71 hits
that were more than 25%.
Note: After submitting my first version of this patch, Andrew Morton
showed me a version written by Daniel Walker, where I picked up
the following ideas from:
1) Using __builtin_constant_p to avoid profiling fixed values.
2) Using __FILE__ instead of instruction pointers.
3) Using the preprocessor to stop all profiling of likely
annotations from vsyscall_64.c.
Thanks to Andrew Morton, Arjan van de Ven, Theodore Tso and Ingo Molnar
for their feed back on this patch.
(*) Not ever unlikely is recorded, those that are used by vsyscalls
(a few of them) had to have profiling disabled.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: deadlock fix in ring_buffer_read_start
The ring_buffer_iter_reset was called from ring_buffer_read_start
where both grabbed the reader_lock.
This patch separates out the internals of ring_buffer_iter_reset
to its own function so that both APIs may grab the reader_lock.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: disable preemption when calling sched_clock()
The ring_buffer_time_stamp still uses sched_clock as its counter.
But it is a bug to call it with preemption enabled. This requirement
should not be pushed to the ring_buffer_time_stamp callers, so
the ring_buffer_time_stamp needs to disable preemption when calling
sched_clock.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: Cleanups on the boot tracer and ftrace
This patch bring some cleanups about the boot tracer headers. The
functions and structures of this tracer have nothing related to ftrace
and should have so their own header file.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: Restructure WARN_ONs in ring_buffer.c
The current WARN_ON macros in ring_buffer.c are quite ugly.
This patch cleans them up and uses a single RB_WARN_ON that returns
the value of the condition. This allows the caller to abort the
function if the condition is true.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: enable/disable ring buffer recording API added
Several kernel developers have requested that there be a way to stop
recording into the ring buffers with a simple switch that can also
be enabled from userspace. This patch addes a new kernel API to the
ring buffers called:
tracing_on()
tracing_off()
When tracing_off() is called, all ring buffers will not be able to record
into their buffers.
tracing_on() will enable the ring buffers again.
These two act like an on/off switch. That is, there is no counting of the
number of times tracing_off or tracing_on has been called.
A new file is added to the debugfs/tracing directory called
tracing_on
This allows for userspace applications to also flip the switch.
echo 0 > debugfs/tracing/tracing_on
disables the tracing.
echo 1 > /debugfs/tracing/tracing_on
enables it.
Note, this does not disable or enable any tracers. It only sets or clears
a flag that needs to be set in order for the ring buffers to write to
their buffers. It is a global flag, and affects all ring buffers.
The buffers start out with tracing_on enabled.
There are now three flags that control recording into the buffers:
tracing_on: which affects all ring buffer tracers.
buffer->record_disabled: which affects an allocated buffer, which may be set
if an anomaly is detected, and tracing is disabled.
cpu_buffer->record_disabled: which is set by tracing_stop() or if an
anomaly is detected. tracing_start can not reenable this if
an anomaly occurred.
The userspace debugfs/tracing/tracing_enabled is implemented with
tracing_stop() but the user space code can not enable it if the kernel
called tracing_stop().
Userspace can enable the tracing_on even if the kernel disabled it.
It is just a switch used to stop tracing if a condition was hit.
tracing_on is not for protecting critical areas in the kernel nor is
it for stopping tracing if an anomaly occurred. This is because userspace
can reenable it at any time.
Side effect: With this patch, I discovered a dead variable in ftrace.c
called tracing_on. This patch removes it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: serialize reader accesses to individual CPU ring buffers
The code in the ring buffer expects only one reader at a time, but currently
it puts that requirement on the caller. This is not strong enough, and this
patch adds a "reader_lock" that serializes the access to the reader API
of the ring buffer.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: add new tracing plugin which can trace full (entry+exit) function calls
This tracer uses the low level function return ftrace plugin to
measure the execution time of the kernel functions.
The first field is the caller of the function, the second is the
measured function, and the last one is the execution time in
nanoseconds.
- v3:
- HAVE_FUNCTION_RET_TRACER have been added. Each arch that support ftrace return
should enable it.
- ftrace_return_stub becomes ftrace_stub.
- CONFIG_FUNCTION_RET_TRACER depends now on CONFIG_FUNCTION_TRACER
- Return traces printing can be used for other tracers on trace.c
- Adapt to the new tracing API (no more ctrl_update callback)
- Correct the check of "disabled" during insertion.
- Minor changes...
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch replaces most of the BUG_ONs in the ring_buffer code with
RB_WARN_ON variants. It adds some more variants as needed for the
replacement. This lets the buffer die nicely and still warn the user.
One BUG_ON remains in the code, and that is because it detects a
bad pointer passed in by the calling function, and not a bug by
the ring buffer code itself.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: stop ftrace_special from recursion
The ftrace_special is used to help debug areas of the kernel.
Because of this, if it is put in certain locations, the fact that
it allows recursion can become a problem if the kernel developer
using does not realize that.
This patch changes ftrace_special to not allow recursion into itself
to make it more robust.
It also changes from preempt disable interrupts disable to prevent
any loss of trace entries.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: removal of unnecessary looping
The lockless part of the ring buffer allows for reentry into the code
from interrupts. A timestamp is taken, a test is preformed and if it
detects that an interrupt occurred that did tracing, it tries again.
The problem arises if the timestamp code itself causes a trace.
The detection will detect this and loop again. The difference between
this and an interrupt doing tracing, is that this will fail every time,
and cause an infinite loop.
Currently, we test if the loop happens 1000 times, and if so, it will
produce a warning and disable the ring buffer.
The problem with this approach is that it makes it difficult to perform
some types of tracing (tracing the timestamp code itself).
Each trace entry has a delta timestamp from the previous entry.
If a trace entry is reserved but and interrupt occurs and traces before
the previous entry is commited, the delta timestamp for that entry will
be zero. This actually makes sense in terms of tracing, because the
interrupt entry happened before the preempted entry was commited, so
one may consider the two happening at the same time. The order is
still preserved in the buffer.
With this idea, instead of trying to get a new timestamp if an interrupt
made it in between the timestamp and the test, the entry could simply
make the delta zero and continue. This will prevent interrupts or
tracers in the timer code from causing the above loop.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix for bug on resize
This patch addresses the bug found here:
http://bugzilla.kernel.org/show_bug.cgi?id=11996
When ftrace converted to the new unified trace buffer, the resizing of
the buffer was not protected as much as it was originally. If tracing
is performed while the resize occurs, then the buffer can be corrupted.
This patch disables all ftrace buffer modifications before a resize
takes place.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: change in trace output
Because the trace buffers are per cpu ring buffers, the start of
the trace can be confusing. If one CPU is very active at the
end of the trace, its history will not go as far back as the
other CPU traces. This means that output for a particular CPU
may not appear for the first part of a trace.
To help annotate what is happening, and to prevent any more
confusion, this patch adds a line that annotates the start of
a CPU buffer output.
For example:
automount-3495 [001] 184.596443: dnotify_parent <-vfs_write
[...]
automount-3495 [001] 184.596449: dput <-path_put
automount-3496 [002] 184.596450: down_read_trylock <-do_page_fault
[...]
sshd-3497 [001] 184.597069: up_read <-do_page_fault
<idle>-0 [000] 184.597074: __exit_idle <-exit_idle
[...]
automount-3496 [002] 184.597257: filemap_fault <-__do_fault
<idle>-0 [003] 184.597261: exit_idle <-smp_apic_timer_interrupt
Note, parsers of a trace output should always ignore any lines that
start with a '#'.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: preemptoff not tested in selftest
Due to the BKL not being preemptable anymore, the selftest of the
preemptoff code can not be tested. It requires that it is called
with preemption enabled, but since the BKL is held, that is no
longer the case.
This patch simply skips those tests if it detects that the context
is not preemptable. The following will now show up in the tests:
Testing tracer preemptoff: can not test ... force PASSED
Testing tracer preemptirqsoff: can not test ... force PASSED
When the BKL is removed, or it becomes preemptable once again, then
the tests will be performed.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: remove obsolete variable in trace_array structure
With the new start / stop method of ftrace, the ctrl variable
in the trace_array structure is now obsolete. Remove it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: Remove the ctrl_update tracer method
With the new quick start/stop method of tracing, the ctrl_update
method is out of date.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
