@@ -307,14 +307,9 @@ 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_irq(&x->wait.lock);
+ spin_unlock_irq(&x->wait.lock);
return true;
}
EXPORT_SYMBOL(completion_done);
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> --- kernel/sched/completion.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)