On 01/04/18 14:21, Andrei Vagin wrote: > On Sun, Apr 01, 2018 at 10:01:41AM +0800, Ian Kent wrote: >> On 01/04/18 09:31, Ian Kent wrote: >>> On 31/03/18 10:28, Andrei Vagin wrote: >>>> In "autofs4: use wait_event_killable", wait_event_interruptible() was >>>> replaced by wait_event_killable(), but in this case we have to use >>>> wake_up() instead of wake_up_interruptible(). >>> >>> Why do you believe wake_up() is needed rather than wake_up_interruptible()? >>> >>> Now that I'm thinking about the wake up I'm wondering if this is in fact >>> what's needed. Rather, I think maybe wake_up_all() is probably the only >>> one that will actually do what's needed. >> >> Ok, so that 1 is the number of exclusive waiters. >> So what is the difference between the two wake_up calls in this case? > > In CRIU, we have the autofs test: > https://github.com/checkpoint-restore/criu/blob/master/test/zdtm/static/autofs.c > > We run CRIU tests on the linux-next kernels and a few days ago this test > started to fail, actually it hangs up. > > I found that wake_up_interruptible() doesn't wake up a thread, which is > waiting. > > try_to_wake_up() has the argument "state", it is the mask of task states > that can be woken. > > For wake_up_interruptible(), state is TASK_INTERRUPTIBLE. > For wake_up(). state is TASK_NORMAL (TASK_INTERRUPTIBLE | > TASK_UNINTERRUPTIBLE) > > If we use wait_event_killable(), the task sleeps in the TASK_KILLABLE > state, so wake_up_interruptible() isn't suitable in this case. > > #define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE) > > I checked that our test passes with this patch. I mean that we had a > real problem and we checked that it is fixed by this patch.
Ahh, I see, wake_up_*() functions do just what they say, they skip TASK_UNINTERRUPTIBLE tasks. Now it makes sense. Acked-by: Ian Kent <ra...@themaw.net> Andrew could you a take this patch as well please. > > Thanks, > Andrei > >> >>> >>> There's an individual wait queue for each mount, there can be multiple >>> waiters for a mount, they all should be woken up when the daemon signals >>> mount completion. >>> >>>> >>>> Cc: Matthew Wilcox <mawil...@microsoft.com> >>>> Cc: Ian Kent <ra...@themaw.net> >>>> Cc: Andrew Morton <a...@linux-foundation.org> >>>> Cc: Stephen Rothwell <s...@canb.auug.org.au> >>>> Signed-off-by: Andrei Vagin <ava...@openvz.org> >>>> --- >>>> fs/autofs4/waitq.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c >>>> index c160e9b3aa0f..be9c3dc048ab 100644 >>>> --- a/fs/autofs4/waitq.c >>>> +++ b/fs/autofs4/waitq.c >>>> @@ -549,7 +549,7 @@ int autofs4_wait_release(struct autofs_sb_info *sbi, >>>> autofs_wqt_t wait_queue_tok >>>> kfree(wq->name.name); >>>> wq->name.name = NULL; /* Do not wait on this queue */ >>>> wq->status = status; >>>> - wake_up_interruptible(&wq->queue); >>>> + wake_up(&wq->queue); >>>> if (!--wq->wait_ctr) >>>> kfree(wq); >>>> mutex_unlock(&sbi->wq_mutex); >>>> >>> >>
