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Date: Sun, 21 Aug 2005 14:59:35 +0400
From: Oleg Nesterov <oleg@tv-sign.ru>
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To: tglx@linutronix.de
Cc: Ingo Molnar <mingo@elte.hu>, Roland McGrath <roland@redhat.com>,
       George Anzinger <george@mvista.com>, linux-kernel@vger.kernel.org,
       Steven Rostedt <rostedt@goodmis.org>,
       "Paul E. McKenney" <paulmck@us.ibm.com>, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] fix send_sigqueue() vs thread exit race
References: <20050818060126.GA13152@elte.hu>
		 <1124495303.23647.579.camel@tglx.tec.linutronix.de>
		 <43076138.C37ED380@tv-sign.ru> <1124617458.23647.643.camel@tglx.tec.linutronix.de>
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Thomas Gleixner wrote:
> 
>  arm timer
>  exit
>  timer event

I think there is another bug here.

CPU_0					CPU_1

release_task:				posix_timer_fn:
	write_lock(tasklist);			lock(timer->it_lock);

	exit_timers:				send_sigxxx();
		lock(timer->it_lock)			read_lock(tasklist);
				
Deadlock.

Dear cc-list, what do you think?

Oleg.