1 files changed, 17 insertions, 2 deletions

diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
index 7052d3fd4e7b..8d0f35debf35 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);