linux-kernel - Re: BUG: enabling psacct breaks fsfreeze

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Message-ID: <20121031121517.GD18424@quack.suse.cz>
Date:	Wed, 31 Oct 2012 13:15:17 +0100
From:	Jan Kara <jack@...e.cz>
To:	Nikola Ciprich <nikola.ciprich@...uxbox.cz>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: BUG: enabling psacct breaks fsfreeze

  Hello,

On Tue 23-10-12 11:43:51, Nikola Ciprich wrote:
> while trying to create consistent backups of KVM guest, I've discovered
> that fsfreeze always hangs.. deeper investigation revealed psacct to be the culprit.
> When psacct is disabled, fsfreeze works fine, when enabled, the command never returns.
> I suppose that the problem is /var is not on separate partition (ie it's same volume
> as /) and psacct isn't able to dump process exit information about fsfreeze command
> thus creating deadlock..
> problem is 100% reproducible on both latest 3.0.x kernel and 3.7-r1c.
> 
> Should more debugging information be needed, I'll be glad to provide whatever I can..
  Thanks for report. Hum, I'm not sure how the deadlock can happen because
AFAIU audit sends a message via netlink to userspace and whatever audit
daemon does with it is its private thing. Can you please run:
  echo w >/proc/sysrq-trigger
after the machine deadlocks and then take dmesg and attach it here? You'll
have to have the shell prepared and use serial console / netconsole to gather
dmesg or try your luck with copying via ssh / netcat.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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