linux-kernel - Re: Hint needed : how to debug sempahore's problem

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Date:	Sun, 2 Sep 2007 23:47:12 +0400
From:	"Alexander Shishkin" <alexander.shishckin@...il.com>
To:	"Philippe De Muyter" <phdm@...qel.be>
Cc:	linux-kernel@...r.kernel.org, uclinux-dev@...inux.org
Subject: Re: Hint needed : how to debug sempahore's problem

On 9/2/07, Philippe De Muyter <phdm@...qel.be> wrote:
> Hi all,
Hi,

> Can someone give me some hint or link for the following question :
>
> I have several processes blocked in 'D' state, and I surmise they are
> waiting for a semaphore (in the `down' routine).  How is it possible :
> - to verify the processes are really blocked on a semaphore,
> - to see which semaphore they are waiting on,
> - to find out which process/driver/whatever holds those semaphores.
I'm sure there might be a better solution, but the easiest one I've
found for myself is enabling sysrq and sending sysrq-p or sysrq-t
combination to the board's console and see the callpaths that lead to
a deadlock (or other incorrect locking situation) in the kernel.

-- 
I like long walks, especially when they are taken by people who annoy me.
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