linux-kernel - Re: shm updates broke UML

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Message-ID: <20110801173206.GA26440@albatros>
Date:	Mon, 1 Aug 2011 21:32:06 +0400
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Richard Weinberger <richard@....at>, serge.hallyn@...onical.com,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net, toralf.foerster@....de
Subject: Re: shm updates broke UML

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.

static void __init do_basic_setup(void)
{
	cpuset_init_smp();
	usermodehelper_init();
	init_tmpfs();
	driver_init();
	init_irq_proc();
	do_ctors();
	do_initcalls(); <<<<
}

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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