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Message-ID: <474F63A5.2000907@serpentine.com>
Date: Thu, 29 Nov 2007 17:13:09 -0800
From: Bryan O'Sullivan <bos@...pentine.com>
To: Larry Finger <Larry.Finger@...inger.net>
CC: LKML <linux-kernel@...r.kernel.org>
Subject: Re: Question regarding mutex locking
Larry Finger wrote:
> If a particular routine needs to lock a mutex, but it may be entered with that mutex already locked,
> would the following code be SMP safe?
>
> hold_lock = mutex_trylock()
The common way to deal with this is first to restructure your function
into two. One always acquires the lock, and the other (often written
with a "__" prefix) never acquires it. The never-acquire code does the
actual work, and the always-acquire function calls it.
You then refactor the callers so that you don't have any code paths on
which you can't predict whether or not the lock will be held.
<b
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