linux-kernel - Re: 2.6.32-rc4ish: task umount blocked for more than 120 seconds after USB drive removal

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Message-ID: <20091104074137.GU8742@kernel.dk>
Date:	Wed, 4 Nov 2009 08:41:37 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Robert Hancock <hancockrwd@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: 2.6.32-rc4ish: task umount blocked for more than 120 seconds
	after USB drive removal

On Tue, Nov 03 2009, Andrew Morton wrote:
> On Tue, 20 Oct 2009 23:26:17 -0600
> Robert Hancock <hancockrwd@...il.com> wrote:
> 
> > Running a post-2.6.32-rc4 git kernel, and just unmounted a USB drive 
> > after writing a bunch of data to it, then pulled the plug after I 
> > thought it had finished unmounting, but apparently it hadn't.. Ran into 
> > a hung task warning that repeats every 120 seconds, the umount command 
> > for the drive is stuck in D state.
> > 
> > The full SysRq-T output is shown at the bottom.. any ideas what it's 
> > waiting for?
> 
> At a guess I'd say the new per-bdi writeback stuff blew up.  Is this
> still happening in current mainline?

It happens in -rc6, it should be fixed in current -git. Robert, can you
try and confirm?

> It's remarkable how much harder these traces are to read post-wordwrapping.

Indeed, I always copy into a new buffer and un-wrap them :/

-- 
Jens Axboe

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