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Subject: Re: [PATCH] autofs4: use wake_up() instead of wake_up_interruptible
From:   Ian Kent <raven@themaw.net>
To:     Andrei Vagin <avagin@openvz.org>
Cc:     autofs@vger.kernel.org, linux-kernel@vger.kernel.org,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>
References: <20180331022839.21277-1-avagin@openvz.org>
 <ebdc431d-cea8-378c-aae5-3b7441bb93c0@themaw.net>
Message-ID: <8d578e49-c1a0-a38d-3b91-f0a07de0089b@themaw.net>
Date:   Sun, 1 Apr 2018 10:01:41 +0800
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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);
>>
>