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. 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); > >> > > >
