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author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-21 10:40:02 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-21 10:40:02 -0800 |
commit | e2defd02717ebc54ae2f4862271a3093665b426a (patch) | |
tree | bb724dc1041b72ac9a241fb9d00aae995fea6236 /kernel/sched/completion.c | |
parent | b5aeca54d0212515d820e5555115e2fc7847a68b (diff) | |
parent | 2636ed5f8d15ff9395731593537b4b3fdf2af24d (diff) | |
download | op-kernel-dev-e2defd02717ebc54ae2f4862271a3093665b426a.zip op-kernel-dev-e2defd02717ebc54ae2f4862271a3093665b426a.tar.gz |
Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
"Thiscontains misc fixes: preempt_schedule_common() and io_schedule()
recursion fixes, sched/dl fixes, a completion_done() revert, two
sched/rt fixes and a comment update patch"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/rt: Avoid obvious configuration fail
sched/autogroup: Fix failure to set cpu.rt_runtime_us
sched/dl: Do update_rq_clock() in yield_task_dl()
sched: Prevent recursion in io_schedule()
sched/completion: Serialize completion_done() with complete()
sched: Fix preempt_schedule_common() triggering tracing recursion
sched/dl: Prevent enqueue of a sleeping task in dl_task_timer()
sched: Make dl_task_time() use task_rq_lock()
sched: Clarify ordering between task_rq_lock() and move_queued_task()
Diffstat (limited to 'kernel/sched/completion.c')
-rw-r--r-- | kernel/sched/completion.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c index 7052d3f..8d0f35d 100644 --- a/kernel/sched/completion.c +++ b/kernel/sched/completion.c @@ -274,7 +274,7 @@ bool try_wait_for_completion(struct completion *x) * first without taking the lock so we can * return early in the blocking case. */ - if (!ACCESS_ONCE(x->done)) + if (!READ_ONCE(x->done)) return 0; spin_lock_irqsave(&x->wait.lock, flags); @@ -297,6 +297,21 @@ EXPORT_SYMBOL(try_wait_for_completion); */ bool completion_done(struct completion *x) { - return !!ACCESS_ONCE(x->done); + if (!READ_ONCE(x->done)) + return false; + + /* + * If ->done, we need to wait for complete() to release ->wait.lock + * otherwise we can end up freeing the completion before complete() + * is done referencing it. + * + * The RMB pairs with complete()'s RELEASE of ->wait.lock and orders + * the loads of ->done and ->wait.lock such that we cannot observe + * the lock before complete() acquires it while observing the ->done + * after it's acquired the lock. + */ + smp_rmb(); + spin_unlock_wait(&x->wait.lock); + return true; } EXPORT_SYMBOL(completion_done); |