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Date: Tue, 3 Jan 2012 10:37:41 -0800
From: Tejun Heo <tj@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Jens Axboe <jaxboe@fusionio.com>
Subject: Re: block: WARN_ON_ONCE(ev->block <= 0) triggered in
 __disk_unblock_events()
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References: <CAO+b5-pig48acSXAYKH09QHCL9EtzTis=mpn=OnE=cvCv+0EzA@mail.gmail.com>
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Hello,

On Sun, Jan 01, 2012 at 05:22:58PM +0000, Bart Van Assche wrote:
> In a workload that involves a lot of scsi_remove_hosts() calls (srp-ha
> patch set stress test) I get the call stack below after about 30 to 50
> iterations. Is this a known issue ? Does this indicate a race
> condition in the block layer ? I can trigger this issue not only with
> 3.2-rc7 but also with 3.1.6. I haven't tried any other kernel versions
> yet.
>
> ------------[ cut here ]------------
> WARNING: at block/genhd.c:1466 __disk_unblock_events+0xf5/0x110()

It's indicating that there were more disk_unblock_events() than
disk_block_events().  Hmmm... weird.  I'll prep a debug patch.

Thanks.

-- 
tejun