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authorTrond Myklebust <Trond.Myklebust@netapp.com>2013-01-27 19:20:49 (GMT)
committerTrond Myklebust <Trond.Myklebust@netapp.com>2013-01-30 22:45:14 (GMT)
commitedd2e36fe8bd3cec4fa67e746d4c4a9246d0830e (patch)
treed44df6639a2431212bcb50f6117ba7b1083dc67d
parentab225417825963b6dc66be7ea80f94ac1378dfdf (diff)
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 <andros@netapp.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
-rw-r--r--net/sunrpc/sched.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index bfa3171..fb20f25 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)

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