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Date: Fri, 01 Jun 2007 09:25:27 -0700
From: Sam Leffler <sam@errno.com>
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To: Artis Caune <Artis.Caune@latnet.lv>
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Cc: hackers@freebsd.org
Subject: Re: stopping callouts
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Artis Caune wrote:
> Hello FreeBSD-hackers!
> 
> what is the right way to stop callout which is initialized with mutex:
>   callout_init_mtx(&callout_function, &my_mtx, 0);
> 
> should I lock mutex before calling callout_drain() or not?
> 
> man page says: callout_drain() is identical to callout_stop() and
> if the callout has an associated mutex, then that mutex must be held 
> when callout_stop() is called.
> 
> 
> /* MOD_UNLOAD */
> 
> MTX_LOCK;
> callout_drain()
> MTX_UNLOCK;

If you use callout_init_mtx then use callout_stop while holding my_mtx; 
if the callout is blocked waiting for my_mtx the request will be discarded.

callout_drain should not be called while holding my_mtx because it can 
sleep.

	Sam