user/sven/linux.git/kernel/sched/completion.c, branch v4.9.53

sched/completion: Serialize completion_done() with complete()

2015-02-18T13:27:40Z

Commit de30ec47302c "Remove unnecessary ->wait.lock serialization when reading completion state" was not correct, without lock/unlock the code like stop_machine_from_inactive_cpu() while (!completion_done()) cpu_relax(); can return before complete() finishes its spin_unlock() which writes to this memory. And spin_unlock_wait(). While at it, change try_wait_for_completion() to use READ_ONCE(). Reported-by: Paul E. McKenney Reported-by: Davidlohr Bueso Tested-by: Paul E. McKenney Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) [ Added a comment with the barrier. ] Cc: Linus Torvalds Cc: Nicholas Mc Guire Cc: raghavendra.kt@linux.vnet.ibm.com Cc: waiman.long@hp.com Fixes: de30ec47302c ("sched/completion: Remove unnecessary ->wait.lock serialization when reading completion state") Link: http://lkml.kernel.org/r/20150212195913.GA30430@redhat.com Signed-off-by: Ingo Molnar

sched/completion: Add lock-free checking of the blocking case

2015-02-04T06:57:37Z

The "thread would block" case can be checked without grabbing ->wait.lock. [ If the check does not return early then grab the lock and recheck. A memory barrier is not needed as complete() and complete_all() imply a barrier. The ACCESS_ONCE() is needed for calls in a loop that, if inlined, could optimize out the re-fetching of x->done. ] Signed-off-by: Nicholas Mc Guire Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1422013307-13200-1-git-send-email-der.herr@hofr.at Signed-off-by: Ingo Molnar

sched/completion: Remove unnecessary ->wait.lock serialization when reading completion state

2015-02-04T06:57:36Z

Signed-off-by: Nicholas Mc Guire Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1421467534-22834-1-git-send-email-der.herr@hofr.at Signed-off-by: Ingo Molnar

sched/completion: Document when to use wait_for_completion_io_*()

2014-11-16T09:58:54Z

As discussed in [1], accounting IO is meant for blkio only. Document that so driver authors won't use them for device io. [1] http://thread.gmane.org/gmane.linux.drivers.i2c/20470 Signed-off-by: Wolfram Sang Signed-off-by: Peter Zijlstra (Intel) Cc: One Thousand Gnomes Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1415098901-2768-1-git-send-email-wsa@the-dreams.de Signed-off-by: Ingo Molnar

sched: Move completion code from core.c to completion.c

2013-11-06T06:49:19Z

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 Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/n/tip-x2y49rmxu5dljt66ai2lcfuw@git.kernel.org Signed-off-by: Ingo Molnar