linux-kernel - Re: Question regarding mutex locking

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Date:	Tue, 27 Nov 2007 22:53:20 -0600
From:	Robert Hancock <hancockr@...w.ca>
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()
> 
> ..
> 
> if (hold_lock)
> 	mutex_unlock()

Not if another task could be acquiring that lock at the same time, which 
is probably the case, otherwise you wouldn't need the mutex. In other 
words, if you're going to do this, you might as well toss the mutex 
entirely as it's about the same effect..

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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