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Date: Thu, 10 May 2007 15:00:05 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Herbert Xu <herbert@gondor.apana.org.au>
CC: "David S. Miller" <davem@davemloft.net>,
       Christoph Hellwig <hch@infradead.org>, Andi Kleen <ak@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       virtualization@lists.osdl.org, lkml <linux-kernel@vger.kernel.org>,
       Chris Wright <chrisw@sous-sol.org>, Ian Pratt <ian.pratt@xensource.com>,
       Christian Limpach <Christian.Limpach@cl.cam.ac.uk>,
       netdev@vger.kernel.org, Jeff Garzik <jeff@garzik.org>,
       Stephen Hemminger <shemminge@linux-foundation.org>,
       Rusty Russell <rusty@rustcorp.com.au>, Valdis.Kletnieks@vt.edu
Subject: Re: [1/2] [NET] link_watch: Move link watch list into net_device
References: <20070504232051.411946839@goop.org> <20070504232121.492190579@goop.org> <20070505091624.GA8890@infradead.org> <463C56D3.8060609@goop.org> <20070505102305.GA12771@gondor.apana.org.au> <463F95C3.60407@goop.org> <20070508121322.GA21647@gondor.apana.org.au>
In-Reply-To: <20070508121322.GA21647@gondor.apana.org.au>
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Herbert Xu wrote:
> [NET] link_watch: Move link watch list into net_device
>
> These days the link watch mechanism is an integral part of the
> network subsystem as it manages the carrier status.  So it now
> makes sense to allocate some memory for it in net_device rather
> than allocating it on demand.

I think there's a problem with one of these two patches.  I've been
noticing that one of my events/X threads has been going into a spin for
about 5 mins after boot.  I added some debugging to
kernel/workqueue.c:run_workqueue, since its that loop which seems to be
spinning due to list corruption.

When I look to see if that loop has iterated for more than 100 times in
one go (which seems unlikely),  I get this:

BUG: cpu 3, count=101 list screwup on c04babe4, func c03217e8
func=linkwatch_event+0x0/0x2a
 [<c0109173>] show_trace_log_lvl+0x1a/0x30
 [<c0109c7f>] show_trace+0x12/0x14
 [<c0109d0c>] dump_stack+0x16/0x18
 [<c0137c25>] run_workqueue+0x97/0x18c
 [<c01386a4>] worker_thread+0xe5/0xf5
 [<c013afe9>] kthread+0x3b/0x62
 [<c0108d47>] kernel_thread_helper+0x7/0x10
 =======================


I wonder if the problem is that the linkwatch_work is being rescheduled
when its already been scheduled, or something like that?

    J
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