[PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[Andrei Vagin]

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().

Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrei Vagin <avagin@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);
-- 
2.13.6

Re: [PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[Ian Kent]

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.

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 <mawilcox@microsoft.com>
> Cc: Ian Kent <raven@themaw.net>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Andrei Vagin <avagin@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);
> 

Re: [PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[Ian Kent]

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?

> 
> 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 <mawilcox@microsoft.com>
>> Cc: Ian Kent <raven@themaw.net>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>> Signed-off-by: Andrei Vagin <avagin@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);
>>
> 

Re: [PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[Andrei Vagin]

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 <mawilcox@microsoft.com>
> >> Cc: Ian Kent <raven@themaw.net>
> >> Cc: Andrew Morton <akpm@linux-foundation.org>
> >> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> >> Signed-off-by: Andrei Vagin <avagin@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);
> >>
> > 
> 

Re: [PATCH] autofs4: use wake_up() instead of wake_up_interruptible

[Ian Kent]

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 <raven@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 <mawilcox@microsoft.com>
>>>> Cc: Ian Kent <raven@themaw.net>
>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>>>> Signed-off-by: Andrei Vagin <avagin@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);
>>>>
>>>
>>