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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-06-29 21:47:04 +0200 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-08-17 17:06:44 +0200 |
commit | dec13c42d21a96adc5d0d25510d0b59775dfd2ec (patch) | |
tree | 03793a9146da912adad6b5b661a3595730b6eaf4 /kernel/sched/completion.c | |
parent | sched: Replace spin_unlock_wait() with lock/unlock pair (diff) | |
download | linux-dec13c42d21a96adc5d0d25510d0b59775dfd2ec.tar.xz linux-dec13c42d21a96adc5d0d25510d0b59775dfd2ec.zip |
completion: Replace spin_unlock_wait() with lock/unlock pair
There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair. This commit therefore replaces the spin_unlock_wait() call in
completion_done() with spin_lock() followed immediately by spin_unlock().
This should be safe from a performance perspective because the lock
will be held only the wakeup happens really quickly.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/sched/completion.c')
-rw-r--r-- | kernel/sched/completion.c | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c index 13fc5ae9bf2f..c9524d2d9316 100644 --- a/kernel/sched/completion.c +++ b/kernel/sched/completion.c @@ -300,6 +300,8 @@ EXPORT_SYMBOL(try_wait_for_completion); */ bool completion_done(struct completion *x) { + unsigned long flags; + if (!READ_ONCE(x->done)) return false; @@ -307,14 +309,9 @@ bool completion_done(struct completion *x) * 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); + spin_lock_irqsave(&x->wait.lock, flags); + spin_unlock_irqrestore(&x->wait.lock, flags); return true; } EXPORT_SYMBOL(completion_done); |