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Re: XFS/md/blkdev warning (was Re: Linux 2.6.26-rc2)

To: Alistair John Strachan <alistair@xxxxxxxxxxxxx>
Subject: Re: XFS/md/blkdev warning (was Re: Linux 2.6.26-rc2)
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Sat, 17 May 2008 11:41:20 -0700 (PDT)
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>, xfs@xxxxxxxxxxx, Neil Brown <neilb@xxxxxxx>, Nick Piggin <npiggin@xxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <alpine.LFD.1.10.0805171131000.3020@woody.linux-foundation.org>
References: <alpine.LFD.1.10.0805120731480.3188@woody.linux-foundation.org> <alpine.LFD.1.10.0805120933310.3019@woody.linux-foundation.org> <20080512164920.GE16217@kernel.dk> <200805171922.56272.alistair@devzero.co.uk> <alpine.LFD.1.10.0805171131000.3020@woody.linux-foundation.org>
Sender: xfs-bounce@xxxxxxxxxxx
User-agent: Alpine 1.10 (LFD 962 2008-03-14)

On Sat, 17 May 2008, Linus Torvalds wrote:
> 
> Do this on the console (and having a serial console or working netconsole 
> is a wonderful thing to log it, because otherwise it will generally just 
> scroll off the screen), and trigger SysRQ-w. That dumps all blocked tasks 
> to the screen.

Another thing to try is to enable lock debugging, and have

        CONFIG_DEBUG_SPINLOCK=y
        CONFIG_DEBUG_MUTEXES=y
        CONFIG_DEBUG_LOCK_ALLOC=y
        CONFIG_PROVE_LOCKING=y
        CONFIG_LOCKDEP=y
        CONFIG_DEBUG_LOCKDEP=y

in your kernel .config file. It has performance implications, of course, 
but it can help debug incorrect locking much more quickly.

                Linus


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