From: Nick Piggin <piggin@cyberone.com.au>
To: "Peter T. Breuer" <ptb@it.uc3m.es>
Cc: Robert White <rwhite@casabyte.com>,
Rik van Riel <riel@imladris.surriel.com>,
David Woodhouse <dwmw2@infradead.org>,
William Lee Irwin III <wli@holomorphy.com>,
"Martin J. Bligh" <mbligh@aracnet.com>,
linux-kernel@vger.kernel.org
Subject: Re: recursive spinlocks. Shoot.
Date: Thu, 22 May 2003 15:09:56 +1000 [thread overview]
Message-ID: <20030522050956.GA273@didi> (raw)
In-Reply-To: <200305220442.h4M4gFM12023@oboe.it.uc3m.es>
On Thu, May 22, 2003 at 06:42:15AM +0200, Peter T. Breuer wrote:
> "Nick Piggin wrote:"
> > Locking is an implementation issue, and as such I think you'll have
> > to come up with a real problem or some real code. You must have some
> > target problem in mind?
>
> I'll butt back in here.
>
snip
>
> The result was a call from the block driver to the md driver with a
> lock held, and a rather unexpected call back from the md driver that
> impotently tried to take the same lock.
>
> Same thread.
>
OK, in this case, it didn't sound like your block driver
expected to be re-entered. Lucky the problem immediately
caused a deadlock ;)
More seriously, lets say you get around the above with
recursive locks:
Thread 1 Thread 2 (on another cpu)
enter the block driver
take the bd lock
issue an md ioctl
take the md lock
enter the block driver
spin on bd lock
automatically call md ioctl
spin on md lock
So the problem needs a rethink.
next prev parent reply other threads:[~2003-05-22 4:57 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-18 9:21 recursive spinlocks. Shoot Peter T. Breuer
2003-05-18 16:30 ` Martin J. Bligh
2003-05-18 16:35 ` William Lee Irwin III
2003-05-18 16:49 ` Arjan van de Ven
2003-05-18 16:54 ` William Lee Irwin III
2003-05-18 17:14 ` Martin J. Bligh
2003-05-18 17:24 ` Peter T. Breuer
2003-05-18 22:34 ` David Woodhouse
2003-05-19 13:37 ` Peter T. Breuer
2003-05-19 13:45 ` Jens Axboe
2003-05-19 13:47 ` Arjan van de Ven
[not found] ` <mailman.1053352200.24653.linux-kernel2news@redhat.com>
2003-05-19 23:54 ` Pete Zaitcev
2003-05-20 0:03 ` viro
2003-05-20 0:03 ` Johannes Erdfelt
2003-05-20 3:12 ` Robert White
2003-05-20 11:59 ` Helge Hafting
2003-05-20 12:23 ` Richard B. Johnson
2003-05-20 21:05 ` Robert White
2003-05-20 21:42 ` Richard B. Johnson
2003-05-20 23:06 ` Robert White
2003-05-21 14:01 ` Richard B. Johnson
2003-05-21 21:56 ` Robert White
2003-05-22 0:13 ` viro
2003-05-22 0:32 ` Robert White
2003-05-22 0:46 ` Carl-Daniel Hailfinger
2003-05-21 5:48 ` Nikita Danilov
2003-05-22 1:00 ` Rik van Riel
2003-05-22 3:11 ` Robert White
2003-05-22 4:04 ` Nick Piggin
2003-05-22 4:42 ` Peter T. Breuer
2003-05-22 5:09 ` Nick Piggin [this message]
2003-05-23 0:19 ` Robert White
2003-05-23 7:22 ` Nikita Danilov
2003-05-23 9:07 ` Helge Hafting
2003-05-23 12:18 ` William Lee Irwin III
2003-05-24 2:39 ` Robert White
2003-05-28 16:50 ` Timothy Miller
2003-05-19 2:05 ` Kevin O'Connor
2003-05-19 6:19 ` Jan Hudec
2003-05-19 10:29 ` Helge Hafting
2003-05-19 11:37 ` Nikita Danilov
2003-05-22 1:21 ` Daniel Phillips
2003-05-19 14:28 ` Martin J. Bligh
2003-05-18 18:13 ` Davide Libenzi
[not found] <20030518182010$0541@gated-at.bofh.it>
2003-05-18 19:09 ` Peter T. Breuer
2003-05-18 19:31 ` Davide Libenzi
2003-05-18 19:49 ` Peter T. Breuer
2003-05-18 20:13 ` Davide Libenzi
2003-05-19 20:47 ` Jan Hudec
[not found] <20030518202013$5297@gated-at.bofh.it>
2003-05-18 23:15 ` Peter T. Breuer
2003-05-18 23:26 ` Davide Libenzi
2003-05-19 12:48 ` Peter T. Breuer
2003-05-19 17:15 ` Davide Libenzi
2003-05-19 17:27 ` Peter T. Breuer
2003-05-19 17:57 ` Alan Cox
2003-05-19 19:51 ` Peter T. Breuer
2003-05-19 20:22 ` Robert White
[not found] <20030520231013$3d77@gated-at.bofh.it>
2003-05-21 14:16 ` Peter T. Breuer
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