linux-kernel - Re: hang in call_usermodehelper

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Message-Id: <201002221053.32560.rusty@rustcorp.com.au>
Date:	Mon, 22 Feb 2010 10:53:32 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: hang in call_usermodehelper_exec()

On Thu, 18 Feb 2010 06:52:34 am Alexey Dobriyan wrote:
> I was stress-testing netns stuff in presence of removing modules.
> 
> Kernel is 2.6.33-rc8-next-20100217+:
> 
> At some point setkey(8) and modprobe hanged:
> 
> 3541 pts/1    D      0:00 /usr/sbin/setkey -f /root/ipcomp-tunnel.setkey
> 3737 pts/2    D      0:00 modprobe -r des_generic sha1_generic md5 hmac xfrm_user crypto_null af_packet xfrm4_mode_beet ipcomp xfrm_ipcomp  xfrm4_tunnel deflate zlib_deflate zlib_inflate esp4 xfrm4_mode_tran

Hmm, looks like sys_delete_module() is stuck trying to re-grab the
module_mutex.  But who's holding it?  We'd need a full task dump to see.

We do a stop_machine with the module mutex held, but not much else.  This
doesn't seem like that.  Do you have tracepoints, or dynamic debug enabled?

Puzzled,
Rusty.
-- 
Away travelling 25Feb-26Mar (6 .de + 1 .pl + 17 .lt + 2 .sg)
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