Commit edd2e36f authored by Trond Myklebust's avatar Trond Myklebust

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
......@@ -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)
......
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