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From: Larry Finger <larry.finger@lwfinger.net>
To: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>,
	Larry Finger <Larry.Finger@lwfinger.net>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: Question regarding mutex locking
Date: Wed, 28 Nov 2007 08:46:51 -0600	[thread overview]
Message-ID: <474D7F5B.9090008@lwfinger.net> (raw)
In-Reply-To: <20071128081031.GF20238@traven>

Matthias Kaehlcke wrote:
> El Tue, Nov 27, 2007 at 10:37:00PM -0600 Larry Finger ha dit:
> 
>> 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()
> 
> this is wont work, a mutex must not be released from another
> context than the one that acquired it.

I thought that mutex_trylock() returned 1 if it got the lock and 0 if not. If that is true, wouldn't
the if statement only unlock if the lock was obtained in this routine?


  reply	other threads:[~2007-11-28 14:46 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-28  4:37 Question regarding mutex locking Larry Finger
2007-11-28  8:10 ` Matthias Kaehlcke
2007-11-28 14:46   ` Larry Finger [this message]
2007-11-28 15:00     ` Matthias Kaehlcke
2007-11-28 15:22 ` Andreas Schwab
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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