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Subject: Re: panic: Stray timeout
To: Konstantin Belousov <kostikbel@gmail.com>
References: <55E2DA91.6080206@FreeBSD.org> <20150830161603.GI2072@kib.kiev.ua>
Cc: FreeBSD Current <freebsd-current@FreeBSD.org>
From: Andriy Gapon <avg@FreeBSD.org>
Message-ID: <55E354DA.9030302@FreeBSD.org>
Date: Sun, 30 Aug 2015 22:09:14 +0300
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On 30/08/2015 19:16, Konstantin Belousov wrote:
> This is strange, I do not think that could be a right explanation of this
> issue.  The taskqueue callout is initialized with the mutex, which means
> that the callout_stop() caller
> - must own the mutex;
> - is synchronous with the callout.
> In other words, callout cannot be running when taskqueue_cancel_timeout()
> calls callout_stop(), it only can be dequeued but the callout function
> is not yet called.  If callout_stop() is performed meantime, between
> dropping callout_cpu lock, and locking the mutex, it must be not run.

Thank you for the explanation.  I am not familiar with the code and I
misinterpreted the manual page and thought that callout_stop() might be unable
to stop the callout even if it was initialized with the mutex.  I see my mistake
now.

-- 
Andriy Gapon