From: Andreas Schwab <schwab@suse.de>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: Question regarding mutex locking
Date: Wed, 28 Nov 2007 16:22:57 +0100 [thread overview]
Message-ID: <jemysy2y3y.fsf@sykes.suse.de> (raw)
In-Reply-To: <474CF06C.8020208@lwfinger.net> (Larry Finger's message of "Tue\, 27 Nov 2007 22\:37\:00 -0600")
Larry Finger <Larry.Finger@lwfinger.net> writes:
> 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()
When two CPUs may enter the critical region at the same time, what is
the point of the mutex? Also, the first CPU may unlock the mutex while
the second one is still inside the critical region.
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
next prev parent reply other threads:[~2007-11-28 15:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-28 4:37 Larry Finger
2007-11-28 8:10 ` Matthias Kaehlcke
2007-11-28 14:46 ` Larry Finger
2007-11-28 15:00 ` Matthias Kaehlcke
2007-11-28 15:22 ` Andreas Schwab [this message]
2007-11-28 15:41 ` Larry Finger
2007-11-28 22:45 ` Jarek Poplawski
2007-11-28 22:56 ` Jarek Poplawski
2007-11-28 23:07 ` Jarek Poplawski
2007-11-28 23:33 ` Stephen Hemminger
2007-11-29 6:40 ` Jarek Poplawski
2007-11-30 1:13 ` Bryan O'Sullivan
[not found] <fa.C9TdvYAhY8SablNc39IpD8WDnNM@ifi.uio.no>
2007-11-28 4:53 ` Robert Hancock
2007-11-28 5:19 ` Larry Finger
2007-11-29 2:34 ` David Schwartz
2007-11-29 7:56 ` Jarek Poplawski
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