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Date: Wed, 13 Jan 2010 20:08:29 -0500
From: Chris Mason <chris.mason@oracle.com>
To: Adrian von Bidder <avbidder@fortytwo.ch>
Cc: Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>,
       linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: task imap:2958 blocked for more than 120 seconds
Message-ID: <20100114010829.GE3428@think>
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	Adrian von Bidder <avbidder@fortytwo.ch>,
	Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>,
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On Mon, Jan 11, 2010 at 09:45:31AM +0100, Adrian von Bidder wrote:
> On Monday 11 January 2010 08.34:36 Adrian von Bidder wrote:
> > "btrfs-vol -b" on an 2T btrfs fs (raid 1 mode over 4 disks) on an arm
> >  CPU  has triggered it several times, so it seems a reliable way to
> >  reproduce this.
> > 
> 
> Found it (Debian kernel 2.6.32 on ARM):
> 
> [78260.386272] INFO: task btrfs-vol:10979 blocked for more than 120 seconds.
> [78260.386306] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [78260.386331] btrfs-vol     D c02b080c     0 10979      1 0x00000001
> [78260.386373] [<c02b080c>] (schedule+0x424/0x488) from [<c02b0c9c>] (schedule_timeout+0x1c/0x244)
> [78260.386408] [<c02b0c9c>] (schedule_timeout+0x1c/0x244) from [<c02b0b10>] (wait_for_common+0xdc/0x178)
> [78260.386611] [<c02b0b10>] (wait_for_common+0xdc/0x178) from [<bf29b880>] (merge_reloc_roots+0x15c/0x1a4 [btrfs])
> [78260.386940] [<bf29b880>] (merge_reloc_roots+0x15c/0x1a4 [btrfs]) from [<bf2a3fd8>] (relocate_block_group+0x548/0x5c8 [btrfs])

Blocking here isn't a huge surprise, relocation can involve some long
held locks.  Does this recover?

-chris
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