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Commit edd2e36f authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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 c05eecf6
(SUNRPC: Don't allow low priority tasks to pre-empt higher priority ones).

Reported-by: default avatarAndy Adamson <andros@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent ab225417

net/sunrpc/sched.c

+17 −1
Original line number Diff line number Diff line
@@ -98,10 +98,26 @@ __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)

{

	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)

{