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Date: Tue, 1 Feb 2011 00:13:01 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: CAI Qian <caiqian@redhat.com>, linux-mm <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org
Subject: Re: kswapd hung tasks in 2.6.38-rc1
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On Mon, Jan 31, 2011 at 02:40:16PM -0800, Dave Hansen wrote:
> Still not a very good data point, but I ran a heavy swap load for an
> hour or so without reproducing this.  But, it happened again after I
> enabled transparent huge pages.  I managed to get a sysrq-t dump out of
> it:
> 
> 	http://sr71.net/~dave/ibm/2.6.38-rc2-hang-0.txt
> 
> khugepaged is one of the three running tasks.  Note, I set both its
> sleep timeouts to zero to stress it out a bit.

sysrq+l? sysrq+t doesn't provide interesting info for running tasks.

> I'll keep trying to reproduce without THP.

BTW, do you have prove locking enabled? With recent git I get a
deadlock inside _raw_spin_unlock_irq with prove locking enabled and it
goes away when I disable it.