From 87ed50036b866db2ec2ba16b2a7aec4a2b0b7c39 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 7 Jan 2013 14:30:46 -0500 Subject: SUNRPC: Ensure we release the socket write lock if the rpc_task exits early If the rpc_task exits while holding the socket write lock before it has allocated an rpc slot, then the usual mechanism for releasing the write lock in xprt_release() is defeated. The problem occurs if the call to xprt_lock_write() initially fails, so that the rpc_task is put on the xprt->sending wait queue. If the task exits after being assigned the lock by __xprt_lock_write_func, but before it has retried the call to xprt_lock_and_alloc_slot(), then it calls xprt_release() while holding the write lock, but will immediately exit due to the test for task->tk_rqstp != NULL. Reported-by: Chris Perl Signed-off-by: Trond Myklebust Cc: stable@vger.kernel.org [>= 3.1] --- net/sunrpc/sched.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'net/sunrpc/sched.c') diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index b4133bd1391..bfa31714581 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -972,8 +972,7 @@ static void rpc_async_release(struct work_struct *work) static void rpc_release_resources_task(struct rpc_task *task) { - if (task->tk_rqstp) - xprt_release(task); + xprt_release(task); if (task->tk_msg.rpc_cred) { put_rpccred(task->tk_msg.rpc_cred); task->tk_msg.rpc_cred = NULL; -- cgit v1.2.3-70-g09d2 From edd2e36fe8bd3cec4fa67e746d4c4a9246d0830e Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Sun, 27 Jan 2013 14:20:49 -0500 Subject: SUNRPC: When changing the queue priority, ensure that we change the owner This fixes a livelock in the xprt->sending queue where we end up never making progress on lower priority tasks because sleep_on_priority() keeps adding new tasks with the same owner to the head of the queue, and priority bumps mean that we keep resetting the queue->owner to whatever task is at the head of the queue. Regression introduced by commit c05eecf636101dd4347b2d8fa457626bf0088e0a (SUNRPC: Don't allow low priority tasks to pre-empt higher priority ones). Reported-by: Andy Adamson Signed-off-by: Trond Myklebust --- net/sunrpc/sched.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'net/sunrpc/sched.c') diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index bfa31714581..fb20f25ddec 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -98,9 +98,25 @@ __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task) list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list); } +static void rpc_rotate_queue_owner(struct rpc_wait_queue *queue) +{ + struct list_head *q = &queue->tasks[queue->priority]; + struct rpc_task *task; + + if (!list_empty(q)) { + task = list_first_entry(q, struct rpc_task, u.tk_wait.list); + if (task->tk_owner == queue->owner) + list_move_tail(&task->u.tk_wait.list, q); + } +} + static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority) { - queue->priority = priority; + if (queue->priority != priority) { + /* Fairness: rotate the list when changing priority */ + rpc_rotate_queue_owner(queue); + queue->priority = priority; + } } static void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid) -- cgit v1.2.3-70-g09d2