Signed-off-by: Andy Adamson<andros@xxxxxxxxxx>
-->Andy
On Mar 19, 2012, at 2:16 PM, Trond Myklebust wrote:
> The problem is that for the case of priority queues, we
> have to assume that __rpc_remove_wait_queue_priority will move new
> elements from the tk_wait.links lists into the queue->tasks[] list.
> We therefore cannot use list_for_each_entry_safe() on queue->tasks[],
> since that will skip these new tasks that __rpc_remove_wait_queue_priority
> is adding.
>
> Without this fix, rpc_wake_up and rpc_wake_up_status will both fail
> to wake up all functions on priority wait queues, which can result
> in some nasty hangs.
>
> Reported-by: Andy Adamson <andros@xxxxxxxxxx>
> Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> net/sunrpc/sched.c | 15 +++++++++++----
> 1 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
> index 1c570a8..994cfea 100644
> --- a/net/sunrpc/sched.c
> +++ b/net/sunrpc/sched.c
> @@ -534,14 +534,18 @@ EXPORT_SYMBOL_GPL(rpc_wake_up_next);
> */
> void rpc_wake_up(struct rpc_wait_queue *queue)
> {
> - struct rpc_task *task, *next;
> struct list_head *head;
>
> spin_lock_bh(&queue->lock);
> head = &queue->tasks[queue->maxpriority];
> for (;;) {
> - list_for_each_entry_safe(task, next, head, u.tk_wait.list)
> + while (!list_empty(head)) {
> + struct rpc_task *task;
> + task = list_first_entry(head,
> + struct rpc_task,
> + u.tk_wait.list);
> rpc_wake_up_task_queue_locked(queue, task);
> + }
> if (head == &queue->tasks[0])
> break;
> head--;
> @@ -559,13 +563,16 @@ EXPORT_SYMBOL_GPL(rpc_wake_up);
> */
> void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
> {
> - struct rpc_task *task, *next;
> struct list_head *head;
>
> spin_lock_bh(&queue->lock);
> head = &queue->tasks[queue->maxpriority];
> for (;;) {
> - list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
> + while (!list_empty(head)) {
> + struct rpc_task *task;
> + task = list_first_entry(head,
> + struct rpc_task,
> + u.tk_wait.list);
> task->tk_status = status;
> rpc_wake_up_task_queue_locked(queue, task);
> }
> --
> 1.7.7.6
>
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