From: Robert Love <rml@ximian.com>
To: Ed L Cashin <ecashin@uga.edu>
Cc: linux-mm@kvack.org
Subject: Re: Documentation/vm/locking: why not hold two PT locks?
Date: Sun, 08 Feb 2004 16:29:38 -0500 [thread overview]
Message-ID: <1076275778.5608.1.camel@localhost> (raw)
In-Reply-To: <8765ehe0cu.fsf@uga.edu>
On Sun, 2004-02-08 at 16:18 -0500, Ed L Cashin wrote:
> Hi. Documentation/vm/locking says one must not simultaneously hold
> the page table lock on mm A and mm B. Is that true? Where is the
> danger?
There isn't a proscribed lock ordering hierarchy, so you can deadlock.
Assume thread 1 obtains the lock on mm A.
Assume thread 2 obtains the lock on mm B.
Assume thread 1 now obtains the lock on mm B - it is taken, so spin
waiting.
Assume thread 2 now obtains the lock on mm A - it too is taken, so spin
waiting.
Boom..
Robert Love
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next prev parent reply other threads:[~2004-02-08 21:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-08 21:18 Documentation/vm/locking: why not hold two PT locks? Ed L Cashin
2004-02-08 21:29 ` Robert Love [this message]
2004-02-08 21:47 ` Ed L Cashin
2004-02-08 22:12 ` Robert Love
2004-02-09 7:44 ` Kanoj Sarcar
2004-02-09 16:19 ` Ed L Cashin
2004-02-09 18:20 ` Kanoj Sarcar
2004-02-09 21:17 ` Ed L Cashin
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