There are places in the kernel where we look up files in fd tables and
access the file structure without holding refereces to the file. So, we
need special care to avoid the race between looking up files in the fd
table and tearing down of the file in another CPU. Otherwise, one might
see a NULL f_dentry or such torn down version of the file. This patch
fixes those special places where such a race may happen.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
By calling send_sig do_SAK is recursively taking the
tasklist_lock, which is silly.
In addition I just audited the kernel and this was the only
place where tasklist_lock is taken inside of task_lock.
So this one line change is a general worthwhile cleanup and
it increases our options on how to fix the ptrace_attach races.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove duplicate call to idr_remove() in ptmx_open.
Error during open can result in call to release_dev() followed by call to
idr_remove(). release_dev already calls idr_remove so the second call can
cause a stack dump in idr_remove()->sub_remove() flagging an attempt to
release an already released entry.
I reproduces this on a machine with a misconfigured X server (attempting to
restart multiple times rapidly) getting the same error as the 1st link
below.
This also seems to be related to:
http://marc.theaimsgroup.com/?l=selinux&m=110536513426735&w=2http://marc.theaimsgroup.com/?l=selinux&m=110596994916785&w=2
The stack dump can occur on close (as well as open) as shown
in the 1st instance above, possible from something like:
process A - open (index=0), open fail to out1,
release_dev calls idr_remove (index 0), down(sem) sleeps
process B - open (index=0), open OK (idr allocated)
process A - wake and call idr_remove on index 0
...
process B - close, release_dev, stack dump on idr_remove (index=0)
because entry already removed
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We changed the wrong symbol. It's tty_insert_flip_string_flags() which is
called from the previously-non-GPL'ed now-inlined tty_insert_flip_char().
Fix that up, and uninline tty_schedule_flip() while we're there.
Cc: Tobias Powalowski <t.powa@gmx.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Alan sayeth "Based on Linus original comments about _GPL we should export
tty_insert_flip_char as EXPORT_SYMBOL because it used to be EXPORT_SYMBOL
equivalent (trivial inline). The other features are new extensions are were
not available to drivers before so need not be provided except as _GPL
functionality as far as I can see."
Addresses http://bugzilla.kernel.org/show_bug.cgi?id=6294
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Fulghum <paulkf@microgate.com>
Cc: Philippe Vouters <Philippe.Vouters@laposte.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I'm not really certain what the thinking was but the code obviously wanted to
walk processes other than just those in it's session, for purposes of do_SAK.
Just walking those tasks that don't have a session assigned sounds at the very
least incomplete.
So modify the code to kill everything in the session and anything else that
might have the tty open. Hopefully this helps if the do_SAK functionality is
ever finished.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We already have the tasklist_lock so there is no need for us to reacquire it
with send_group_sig_info. reader/writer locks allow multiple readers and thus
recursion so the old code was ok just wastful.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
this changes if() BUG(); constructs to BUG_ON() which is
cleaner, contains unlikely() and can better optimized away.
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Add a couple of 'const' qualifiers to the TTY flip buffer APIs, where
appropriate.
Signed-off-by: Thomas Koeller <thomas@koeller.dyndns.org>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Semaphore to mutex conversion.
The conversion was generated via scripts, and the result was validated
automatically via a script as well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Comment out debug code in tty receive buffering. For performance reasons
(I'll keep it enabled in -mm).
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix hole where tty structure can be released when reference count is non
zero. Existing code can sleep without tty_sem protection between deciding
to release the tty structure (setting local variables tty_closing and
otty_closing) and setting TTY_CLOSING to prevent further opens. An open
can occur during this interval causing release_dev() to free the tty
structure while it is still referenced.
This should fix bugzilla.kernel.org [Bug 6041] New: Unable to handle kernel
paging request
In Bug 6041, tty_open() oopes on accessing the tty structure it has
successfully claimed. Bug was on SMP machine with the same tty being
opened and closed by multiple processes, and DEBUG_PAGEALLOC enabled.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Prevent stalled processing of received data when a driver allocates tty
buffer space but does not immediately follow the allocation with more data
and a call to schedule receive tty processing. (example: hvc_console) This
bug was introduced by the first locking patch for the new tty buffering.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Change locking in the new tty buffering facility from using tty->read_lock,
which is currently ignored by drivers and thus ineffective. New locking
uses a new tty buffering specific lock enforced centrally in the tty
buffering code.
Two drivers (esp and cyclades) are updated to use the tty buffering
functions instead of accessing tty buffering internals directly. This is
required for the new locking to work.
Minor checks for NULL buffers added to
tty_prepare_flip_string/tty_prepare_flip_string_flags
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix typos in new tty buffering that incorrectly
access and update buffers in pending queue.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.
This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.
When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.
For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).
Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.
The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.
I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.
Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real. That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.
Description:
tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification]. It
does now also return the number of chars inserted
There are also
tty_buffer_request_room(tty, len)
which asks for a buffer block of the length requested and returns the space
found. This improves efficiency with hardware that knows how much to
transfer.
and tty_insert_flip_string_flags(tty, str, flags, len)
to insert a string of characters and flags
For a smart interface the usual code is
len = tty_request_buffer_room(tty, amount_hardware_says);
tty_insert_flip_string(tty, buffer_from_card, len);
More description!
At the moment tty buffers are attached directly to the tty. This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)
I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers. This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.
So far so good. Lots of drivers reference tty->flip.*. Several of them also
call directly and unsafely into function pointers it provides. This will all
break. Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.
At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say
int tty_buffer_request_room(tty, size)
Try and ensure at least size bytes are available, returns actual room (may be
zero). At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative. (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space. The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.
int tty_insert_flip_char(tty, ch, flag)
As before insert a character if there is room. Now returns 1 for success, 0
for failure.
int tty_insert_flip_string(tty, str, len)
Insert a block of non error characters. Returns the number inserted.
int tty_prepare_flip_string(tty, strptr, len)
Adjust the buffer to allow len characters to be added. Returns a buffer
pointer in strptr and the length available. This allows for hardware that
needs to use functions like insl or mencpy_fromio.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This is the drivers/char/ part of the big kfree cleanup patch.
Remove pointless checks for NULL prior to calling kfree() in drivers/char/.
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Now that RCU applied on 'struct file' seems stable, we can place f_rcuhead
in a memory location that is not anymore used at call_rcu(&f->f_rcuhead,
file_free_rcu) time, to reduce the size of this critical kernel object.
The trick I used is to move f_rcuhead and f_list in an union called f_u
The callers are changed so that f_rcuhead becomes f_u.fu_rcuhead and f_list
becomes f_u.f_list
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The previous patch adding the ability to nest struct class_device
changed the paramaters to the call class_device_create(). This patch
fixes up all in-kernel users of the function.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
With the use of RCU in files structure, the look-up of files using fds can now
be lock-free. The lookup is protected by rcu_read_lock()/rcu_read_unlock().
This patch changes the readers to use lock-free lookup.
Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically. Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure. This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct. It also changes all
the users to refer to the file table using files_fdtable() macro. Subsequent
applciation of RCU becomes easier after this.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The idea of this patch is to lock both sides of a ptmx/pty pair during line
discipline changing. This is needed to ensure that say a poll on one side of
the pty doesn't occur while the line discipline is actively being changed.
This resulted in an oops reported on lkml, see:
http://marc.theaimsgroup.com/?l=linux-kernel&m=111342171410005&w=2
A 'hacky' approach was previously implmemented which served to eliminate the
poll vs. line discipline changing race. However, this patch takes a more
general approach to the issue. The patch only adds locking on a less often
used path, the line-discipline changing path, as opposed to locking the
ptmx/pty pair on read/write/poll paths.
The patch below, takes both ldisc locks in either order b/c the locks are both
taken under the same spinlock(). I thought about locking the ptmx/pty
separately, such as master always first but that introduces a 3 way deadlock.
For example, process 1 does a blocking read on the slave side. Then, process
2 does an ldisc change on the slave side, which acquires the master ldisc lock
but not the slave's. Finally, process 3 does a write which blocks on the
process 2's ldisc reference.
This patch does introduce some changes in semantics. For example, a line
discipline change on side 'a' of a ptmx/pty pair, will now wait for a
read/write to complete on the other side, or side 'b'. The current behavior
is to simply wait for any read/writes on only side 'a', not both sides 'a' and
'b'. I think this behavior makes sense, but I wanted to point it out.
I've tested the patch with a bunch of read/write/poll while changing the line
discipline out from underneath.
This patch obviates the need for the above "hide the problem" patch.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
this is the last serial driver not using initcalls.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: <jeff@uclinux.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Use msleep_interruptible() instead of schedule_timeout() in send_break() to
guarantee the task delays as expected. Change @duration's units to
milliseconds, and modify arguments in callers appropriately. Patch is
compile-tested.
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Domen Puncer <domen@coderock.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
It's a bit strange to see tty_register_ldisc call in modules' exit
functions.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
