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-rw-r--r--kernel/locking/rwsem-xadd.c17
1 files changed, 7 insertions, 10 deletions
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index 80b05ac0f015..fcbf75ac3dcb 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -194,17 +194,15 @@ __rwsem_mark_wake(struct rw_semaphore *sem,
waiter = list_entry(next, struct rwsem_waiter, list);
next = waiter->list.next;
tsk = waiter->task;
+
+ wake_q_add(wake_q, tsk);
/*
- * Make sure we do not wakeup the next reader before
- * setting the nil condition to grant the next reader;
- * otherwise we could miss the wakeup on the other
- * side and end up sleeping again. See the pairing
- * in rwsem_down_read_failed().
+ * Ensure that the last operation is setting the reader
+ * waiter to nil such that rwsem_down_read_failed() cannot
+ * race with do_exit() by always holding a reference count
+ * to the task to wakeup.
*/
- smp_mb();
- waiter->task = NULL;
- wake_q_add(wake_q, tsk);
- put_task_struct(tsk);
+ smp_store_release(&waiter->task, NULL);
} while (--loop);
sem->wait_list.next = next;
@@ -228,7 +226,6 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
/* set up my own style of waitqueue */
waiter.task = tsk;
waiter.type = RWSEM_WAITING_FOR_READ;
- get_task_struct(tsk);
raw_spin_lock_irq(&sem->wait_lock);
if (list_empty(&sem->wait_list))