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Message-ID: <4E36E5AB.5000509@arm.com>
Date: Mon, 01 Aug 2011 18:43:07 +0100
From: Marc Zyngier <marc.zyngier@arm.com>
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To: Vasiliy Kulikov <segoon@openwall.com>
CC: Richard Weinberger <richard@nod.at>,
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	<user-mode-linux-devel@lists.sourceforge.net>,
        "toralf.foerster@gmx.de" <toralf.foerster@gmx.de>
Subject: Re: shm updates broke UML
References: <201108011541.59640.richard@nod.at> <20110801134911.GA11705@albatros> <43e4e9e98b32d3d3eb06ab837a019ad8@localhost> <20110801171042.GA25954@albatros> <08cf4697685ecd9bcb7e4eefe516f2ee@localhost> <20110801172452.GA26190@albatros> <20110801173206.GA26440@albatros>
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On 01/08/11 18:32, Vasiliy Kulikov wrote:
> Marc,
> 
> On Mon, Aug 01, 2011 at 21:24 +0400, Vasiliy Kulikov wrote:
>> On Mon, Aug 01, 2011 at 19:19 +0200, Marc Zyngier wrote:
>>> Here you go (sorry about the line wrapping, damned webmail...):
>>
>> Thank you!  Now I see that the problem is rw_mutex is not initialized:
>>
>> 	down_write(&shm_ids(ns).rw_mutex);
>>
>> void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
>> {
>>     ...
>> 	if (sem->activity == 0 && list_empty(&sem->wait_list)) {
>>                                          ^^^^^^^^^^^^^^^ is NULL
>>
>> Wtf - ipc namespace should be fully initialized for the moment of
>> threads run...
> 
> Does ARM try to run _any_ threads before do_initcalls()?  IPC
> initialization is initcall, so any thread before do_initcalls() is a
> dependency bug.

I don't think it does anything different from other architectures.
The crash I'm observing seem to be from kworker, which is created from
an early_initcall (kernel/workqueue.c).

This looks very much like a generic problem to me.

	M.
-- 
Jazz is not dead. It just smells funny...