A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-28 18:51:56 -04:00
Code Issues Projects Releases Packages Wiki Activity

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

Browse source 
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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Nicholas Mc Guire 2015-01-23 12:41:47 +01:00 • committed by Ingo Molnar
commit 7c34e3180a
1 changed files with 9 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

9
kernel/sched/completion.c
View file

@ -268,6 +268,15 @@ bool try_wait_for_completion(struct completion *x)
unsigned long flags;
int ret = 1;
/*
* Since x->done will need to be locked only
* in the non-blocking case, we check x->done
* first without taking the lock so we can
* return early in the blocking case.
*/
if (!ACCESS_ONCE(x->done))
return 0;
spin_lock_irqsave(&x->wait.lock, flags);
if (!x->done)
ret = 0;