From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Trond Myklebust , Luis Henriques Subject: [PATCH 012/102] SUNRPC: Add barriers to ensure read ordering in rpc_wake_up_task_queue_locked Date: Mon, 8 Apr 2013 10:49:27 +0100 Message-Id: <1365414657-29191-13-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1365414657-29191-1-git-send-email-luis.henriques@canonical.com> References: <1365414657-29191-1-git-send-email-luis.henriques@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.5.7.10 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Trond Myklebust commit 1166fde6a923c30f4351515b6a9a1efc513e7d00 upstream. 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 Signed-off-by: Luis Henriques --- net/sunrpc/sched.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index 85b9235..72d89e1 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -143,6 +143,8 @@ 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", @@ -399,8 +401,11 @@ 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); + } } /* -- 1.8.1.2