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Subject[PATCH RFC v2] sched: completion: locks should not be needed for reading completion state
Date
Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
---

v2: proper subsystem tag in subject line

The ACCESS_ONCE is needed for calls in a loop that, if inlined, could
optimize out the re-fetching of x->done. An explicit memory barrier is
not needed as complete() and complete_all() imply a barrier.

kernel/sched/completion.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
index 607f852..7c5cd70 100644
--- a/kernel/sched/completion.c
+++ b/kernel/sched/completion.c
@@ -288,13 +288,6 @@ EXPORT_SYMBOL(try_wait_for_completion);
*/
bool completion_done(struct completion *x)
{
- unsigned long flags;
- int ret = 1;
-
- spin_lock_irqsave(&x->wait.lock, flags);
- if (!x->done)
- ret = 0;
- spin_unlock_irqrestore(&x->wait.lock, flags);
- return ret;
+ return !ACCESS_ONCE(x->done);
}
EXPORT_SYMBOL(completion_done);
--
1.7.10.4


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