From: Trond Myklebust Date: Sun, 27 Jan 2013 19:20:49 +0000 (-0500) Subject: SUNRPC: When changing the queue priority, ensure that we change the owner X-Git-Tag: Ubuntu-5.0.0-8.9~14407^2~1 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=edd2e36fe8bd3cec4fa67e746d4c4a9246d0830e;p=mirror_ubuntu-disco-kernel.git 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 --- diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index bfa31714581f..fb20f25ddec9 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)