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).

Trond Myklebust committed 13 years ago

Commit edd2e361 parent ab225411 file · +17 −1Browse files

Unified · Split

net/sunrpc/sched.c+17−1

@@ -98,9 +98,25 @@ __rpc_add_timer(struct rpc_wait_queue queue, struct rpc_task task) · 97 unmodified lines
98	list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);	98	list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
99	}	99	}
100		100
		101	static void rpc_rotate_queue_owner(struct rpc_wait_queue *queue)
		102	{
		103	struct list_head *q = &queue->tasks[queue->priority];
		104	struct rpc_task *task;
		105
		106	if (!list_empty(q)) {
		107	task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
		108	if (task->tk_owner == queue->owner)
		109	list_move_tail(&task->u.tk_wait.list, q);
		110	}
		111	}
		112
101	static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)	113	static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
102	{	114	{
103	queue->priority = priority;	115	if (queue->priority != priority) {
		116	/* Fairness: rotate the list when changing priority */
		117	rpc_rotate_queue_owner(queue);
		118	queue->priority = priority;
		119	}
104	}	120	}
105		121
106	static void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid)	122	static void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid)