From: Larry Finger <larry.finger@lwfinger.net>
To: Andreas Schwab <schwab@suse.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: Question regarding mutex locking
Date: Wed, 28 Nov 2007 09:41:22 -0600 [thread overview]
Message-ID: <474D8C22.7010902@lwfinger.net> (raw)
In-Reply-To: <jemysy2y3y.fsf@sykes.suse.de>
Andreas Schwab wrote:
> 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.
Thank you for that answer. I think that I'm finally beginning to understand.
Larry
next prev parent reply other threads:[~2007-11-28 15:41 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
2007-11-28 15:00 ` Matthias Kaehlcke
2007-11-28 15:22 ` Andreas Schwab
2007-11-28 15:41 ` Larry Finger [this message]
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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