linux-kernel - Re: Please add to stable: module: don't unlink the module until we've removed all exposure.

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Date:	Tue, 04 Jun 2013 15:26:28 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Ben Greear <greearb@...delatech.com>,
	Joe Lawrence <joe.lawrence@...atus.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org
Subject: Re: Please add to stable:  module: don't unlink the module until we've removed all exposure.

Ben Greear <greearb@...delatech.com> writes:
>> It at least works around the problem for me as well.  But, a more rare
>> migration/[0-3] (I think) related lockup still exists in 3.9.4 for me,
>> so I will also try applying that other kobject patch and continue testing
>> today...
>
> Well, that other kobject patch is already in 3.9.4, so I think it's still
> a good idea to include the
> "module: don't unlink the module until we've removed all exposure."
> patch in stable.  I have a decent test case to reproduce the crash, so if someone
> wants me to test other patches instead, then I will do so.

OK, I cannot reproduce on 3.9.4.  I #if 0'd out the WARNs in sysfs and
kobject, and did this (which reliably broke on 3.8):

# M=`modinfo -F filename e1000`
# for i in `seq 10000`; do insmod $M; rmmod e1000; done >/dev/null 2>&1 & for i in `seq 10000`; do insmod $M; rmmod e1000; done > /dev/null 2>&1 & for i in `seq 10000`; do insmod $M; rmmod e1000; done > /dev/null 2>&1 & for i in `seq 10000`; do insmod $M; rmmod e1000; done >/dev/null 2>&1 &
# 

This was under kvm, 4-way SMP, init=/bin/bash.

Do you have a backtrace of the 3.9.4 crash?  You can add "CFLAGS_module.o
= -O0" to get a clearer backtrace if you want...

Thanks,
Rusty.
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