Commit 1166fde6 authored by Trond Myklebust's avatar Trond Myklebust

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org
parent 24028672
......@@ -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);
}
}
/*
......
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