Merge tag 'tags/cleanup-3.11-3' into mvebu/regmap

[~andy/linux] / net / sunrpc / sched.c

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index fb20f25ddec9b70c805ad65d675441d02b62055b..5356b120dbf8e2fe61ba88081d1fab1941f135a9 100644 (file)
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -180,6 +180,8 @@ static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
                list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
        task->tk_waitqueue = queue;
        queue->qlen++;
+       /* barrier matches the read in rpc_wake_up_task_queue_locked() */
+       smp_wmb();
        rpc_set_queued(task);
 
        dprintk("RPC: %5u added to queue %p \"%s\"\n",
@@ -322,11 +324,17 @@ EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
  * Note: If the task is ASYNC, and is being made runnable after sitting on an
  * rpc_wait_queue, this must be called with the queue spinlock held to protect
  * the wait queue operation.
+ * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
+ * which is needed to ensure that __rpc_execute() doesn't loop (due to the
+ * lockless RPC_IS_QUEUED() test) before we've had a chance to test
+ * the RPC_TASK_RUNNING flag.
  */
 static void rpc_make_runnable(struct rpc_task *task)
 {
+       bool need_wakeup = !rpc_test_and_set_running(task);
+
        rpc_clear_queued(task);
-       if (rpc_test_and_set_running(task))
+       if (!need_wakeup)
                return;
        if (RPC_IS_ASYNC(task)) {
                INIT_WORK(&task->u.tk_work, rpc_async_schedule);
@@ -430,8 +438,11 @@ static void __rpc_do_wake_up_task(struct rpc_wait_queue *queue, struct rpc_task
  */
 static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue, struct rpc_task *task)
 {
-       if (RPC_IS_QUEUED(task) && task->tk_waitqueue == queue)
-               __rpc_do_wake_up_task(queue, task);
+       if (RPC_IS_QUEUED(task)) {
+               smp_rmb();
+               if (task->tk_waitqueue == queue)
+                       __rpc_do_wake_up_task(queue, task);
+       }
 }
 
 /*