On Mar 16, 2012, at 11:21 AM, Myklebust, Trond wrote:
> On Fri, 2012-03-16 at 11:13 -0400, Andy Adamson wrote:
>> On Thu, Mar 15, 2012 at 8:10 PM, Myklebust, Trond
>> <Trond.Myklebust@xxxxxxxxxx> wrote:
>>> On Thu, 2012-03-15 at 14:40 -0400, andros@xxxxxxxxxx wrote:
>>>> From: Andy Adamson <andros@xxxxxxxxxx>
>>>>
>>>> Signed-off-by: Andy Adamson <andros@xxxxxxxxxx>
>>>> ---
>>>> include/linux/sunrpc/sched.h | 1 +
>>>> net/sunrpc/sched.c | 27 +++++++++++++++++++++++++++
>>>> 2 files changed, 28 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
>>>> index dc0c3cc..fce0873 100644
>>>> --- a/include/linux/sunrpc/sched.h
>>>> +++ b/include/linux/sunrpc/sched.h
>>>> @@ -235,6 +235,7 @@ void rpc_sleep_on_priority(struct rpc_wait_queue *,
>>>> void rpc_wake_up_queued_task(struct rpc_wait_queue *,
>>>> struct rpc_task *);
>>>> void rpc_wake_up(struct rpc_wait_queue *);
>>>> +void rpc_drain_queue(struct rpc_wait_queue *);
>>>> struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *);
>>>> struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *,
>>>> bool (*)(struct rpc_task *, void *),
>>>> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
>>>> index 1c570a8..11928ff 100644
>>>> --- a/net/sunrpc/sched.c
>>>> +++ b/net/sunrpc/sched.c
>>>> @@ -551,6 +551,33 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
>>>> EXPORT_SYMBOL_GPL(rpc_wake_up);
>>>>
>>>> /**
>>>> + * rpc_drain_queue - empty the queue and wake up all rpc_tasks
>>>> + * @queue: rpc_wait_queue on which the tasks are sleeping
>>>> + *
>>>> + * Grabs queue->lock
>>>> + */
>>>> +void rpc_drain_queue(struct rpc_wait_queue *queue)
>>>> +{
>>>> + struct rpc_task *task;
>>>> + struct list_head *head;
>>>> +
>>>> + spin_lock_bh(&queue->lock);
>>>> + head = &queue->tasks[queue->maxpriority];
>>>> + for (;;) {
>>>> + while (!list_empty(head)) {
>>>> + task = list_entry(head->next, struct rpc_task,
>>>> + u.tk_wait.list);
>>>> + rpc_wake_up_task_queue_locked(queue, task);
>>>> + }
>>>> + if (head == &queue->tasks[0])
>>>> + break;
>>>> + head--;
>>>> + }
>>>> + spin_unlock_bh(&queue->lock);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(rpc_drain_queue);
>>>> +
>>>
>>> Confused... How is this function any different from rpc_wake_up()?
>>
>> Because it actually drains the queues where rpc_wake_up does not. See
>> the attached output where I added the same printks to both
>> rpc_drain_queue and rpc_wake_up.
>
> So you are seeing a bug in rpc_wake_up()? I'm surprised; a bug of that
> magnitude should have caused a lot of hangs. Can you please look into
> what is happening.
OK. Didn't know it was a bug - just thought the comment was off...
-->Andy
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
>
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