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authorTrond Myklebust <Trond.Myklebust@netapp.com>2013-03-25 11:23:40 -0400
committerTrond Myklebust <Trond.Myklebust@netapp.com>2013-03-25 11:23:40 -0400
commit1166fde6a923c30f4351515b6a9a1efc513e7d00 (patch)
treec324a24baa26658651d2e1ecbf2771da569ff38b /net/sunrpc
parent240286725d854331422cb15957f8d9bf2741d4e3 (diff)
downloadlinux-1166fde6a923c30f4351515b6a9a1efc513e7d00.tar.gz
SUNRPC: Add barriers to ensure read ordering in rpc_wake_up_task_queue_locked
We need to be careful when testing task->tk_waitqueue in rpc_wake_up_task_queue_locked, because it can be changed while we are holding the queue->lock. By adding appropriate memory barriers, we can ensure that it is safe to test task->tk_waitqueue for equality if the RPC_TASK_QUEUED bit is set. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'net/sunrpc')
-rw-r--r--net/sunrpc/sched.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index fb20f25ddec..f8529fc8e54 100644
--- 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",
@@ -430,8 +432,11 @@ 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);
+ }
}
/*