In theory, COMPLETION_INITIALIZER_ONSTACK() should never affect the
stack allocation of the caller. However, on some compilers, a temporary
structure was allocated for the return value of
COMPLETION_INITIALIZER_ONSTACK().
For example in write_journal() with LOCKDEP_COMPLETIONS=y (GCC is 7.1.1):
io_comp.comp = COMPLETION_INITIALIZER_ONSTACK(io_comp.comp);
2462: e8 00 00 00 00 callq 2467 <write_journal+0x47>
2467: 48 8d 85 80 fd ff ff lea -0x280(%rbp),%rax
246e: 48 c7 c6 00 00 00 00 mov $0x0,%rsi
2475: 48 c7 c2 00 00 00 00 mov $0x0,%rdx
x->done = 0;
247c: c7 85 90 fd ff ff 00 movl $0x0,-0x270(%rbp)
2483: 00 00 00
init_waitqueue_head(&x->wait);
2486: 48 8d 78 18 lea 0x18(%rax),%rdi
248a: e8 00 00 00 00 callq 248f <write_journal+0x6f>
if (commit_start + commit_sections <= ic->journal_sections) {
248f: 41 8b 87 a8 00 00 00 mov 0xa8(%r15),%eax
io_comp.comp = COMPLETION_INITIALIZER_ONSTACK(io_comp.comp);
2496: 48 8d bd e8 f9 ff ff lea -0x618(%rbp),%rdi
249d: 48 8d b5 90 fd ff ff lea -0x270(%rbp),%rsi
24a4: b9 17 00 00 00 mov $0x17,%ecx
24a9: f3 48 a5 rep movsq %ds:(%rsi),%es:(%rdi)
if (commit_start + commit_sections <= ic->journal_sections) {
24ac: 41 39 c6 cmp %eax,%r14d
io_comp.comp = COMPLETION_INITIALIZER_ONSTACK(io_comp.comp);
24af: 48 8d bd 90 fd ff ff lea -0x270(%rbp),%rdi
24b6: 48 8d b5 e8 f9 ff ff lea -0x618(%rbp),%rsi
24bd: b9 17 00 00 00 mov $0x17,%ecx
24c2: f3 48 a5 rep movsq %ds:(%rsi),%es:(%rdi)
We can obviously see the temporary structure allocated, and the compiler
also does two meaningless memcpy with "rep movsq".
And according to:
https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement-Exprs
The return value of a statement expression is returned by value, so the
temporary variable is created in COMPLETION_INITIALIZER_ONSTACK(), and
that's why the temporary structures are allocted.
To fix this, make the brace block in COMPLETION_INITIALIZER_ONSTACK()
return a pointer and dereference it outside the block rather than return
the whole structure, in this way, we are able to teach the compiler not
to do the unnecessary stack allocation.
This could also reduce the stack size even if !LOCKDEP, for example in
write_journal(), compiled with gcc 7.1.1, the result of command:
objdump -d drivers/md/dm-integrity.o | ./scripts/checkstack.pl x86
before:
0x0000246a write_journal [dm-integrity.o]: 696
after:
0x00002b7a write_journal [dm-integrity.o]: 296
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/20170823152542.5150-3-boqun.feng@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
'complete' is an adjective and LOCKDEP_COMPLETE sounds like 'lockdep is complete',
so pick a better name that uses a noun.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/1502960261-16206-3-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Although wait_for_completion() and its family can cause deadlock, the
lock correctness validator could not be applied to them until now,
because things like complete() are usually called in a different context
from the waiting context, which violates lockdep's assumption.
Thanks to CONFIG_LOCKDEP_CROSSRELEASE, we can now apply the lockdep
detector to those completion operations. Applied it.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-10-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
All users are converted over to reinit_completion(). Remove the old
macro now.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For the casual device driver writer, it is hard to remember when to use
init_completion (to init a completion structure) or INIT_COMPLETION (to
*reinit* a completion structure). Furthermore, while all other
completion functions exepct a pointer as a parameter, INIT_COMPLETION
does not. To make it easier to remember which function to use and to
make code more readable, introduce a new inline function with the proper
name and consistent argument type. Update the kernel-doc for
init_completion while we are here.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org> (personally at LCE13)
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Completions already have their own header file: linux/completion.h
Move the implementation out of kernel/sched/core.c and into its own
file: kernel/sched/completion.c.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-x2y49rmxu5dljt66ai2lcfuw@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Most of the stuff from kernel/sched.c was moved to kernel/sched/core.c long time
back and the comments/Documentation never got updated.
I figured it out when I was going through sched-domains.txt and so thought of
fixing it globally.
I haven't crossed check if the stuff that is referenced in sched/core.c by all
these files is still present and hasn't changed as that wasn't the motive behind
this patch.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/cdff76a265326ab8d71922a1db5be599f20aad45.1370329560.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The only difference between wait_for_completion[_timeout]() and
wait_for_completion_io[_timeout]() is that the latter calls
io_schedule_timeout() instead of schedule_timeout() so that the caller
is accounted as waiting for IO, not just sleeping.
These functions can be used for correct iowait time accounting when the
completion struct is actually used for waiting for IO (e.g. completion
of a bio request in the block layer).
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
wait_for_completion_*_timeout() can return:
0: if the wait timed out
-ve: if the wait was interrupted
+ve: if the completion was completed.
As they currently return an 'unsigned long', the last two cases
are not easily distinguished which can easily result in buggy
code, as is the case for the recently added
wait_for_completion_interruptible_timeout() call in
net/sunrpc/cache.c
So change them both to return 'long'. As MAX_SCHEDULE_TIMEOUT
is LONG_MAX, a large +ve return value should never overflow.
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110105125016.64ccab0e@notabene.brown>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add more wait, wake, and completion interfaces to the device-drivers
docbook.
Fix kernel-doc notation in the added files.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add missing _killable_timeout variant for wait_for_completion that will
return when a timeout expires or the task is killed.
CC: Ingo Molnar <mingo@elte.hu>
CC: Andreas Herrmann <andreas.herrmann3@amd.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Sage Weil <sage@newdream.net>
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>
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>
XFS object flushing doesn't quite match existing completion semantics. It
mixed exclusive access with completion. That is, we need to mark an object as
being flushed before flushing it to disk, and then block any other attempt to
flush it until the completion occurs. We do this but adding an extra count to
the completion before we start using them. However, we still need to
determine if there is a completion in progress, and allow no-blocking attempts
fo completions to decrement the count.
To do this we introduce:
int try_wait_for_completion(struct completion *x)
returns a failure status if done == 0, otherwise decrements done
to zero and returns a "started" status. This is provided
to allow counted completions to begin safely while holding
object locks in inverted order.
int completion_done(struct completion *x)
returns 1 if there is no waiter, 0 if there is a waiter
(i.e. a completion in progress).
This replaces the use of semaphores for providing this exclusion
and completion mechanism.
SGI-PV: 981498
SGI-Modid: xfs-linux-melb:xfs-kern:31816a
Signed-off-by: David Chinner <david@fromorbit.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Jeff Dike noticed that wait_for_completion_interruptible()'s prototype
had a mismatched fastcall.
Fix this by removing the fastcall attributes from all the completion APIs.
Found-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Clean up lockdep on-stack-completion initializer. (This also removes the
dependency on waitqueue_lock_key.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
lockdep needs to have the waitqueue lock initialized for on-stack waitqueues
implicitly initialized by DECLARE_COMPLETION(). Introduce the API.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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!
Boqun Feng
Byungchul Park
Wolfram Sang
Peter Zijlstra
Viresh Kumar
Vladimir Davydov
NeilBrown
Randy Dunlap
Sage Weil
Kevin Diggs
Dave Chinner
Matthew Wilcox
Ingo Molnar
Linus Torvalds