Date: Thu, 31 May 2007 16:24:55 +0200
From: Ingo Molnar <mingo@elte.hu>
To: john stultz <johnstul@us.ibm.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
       Steven Rostedt <rostedt@goodmis.org>,
       Sripathi Kodi <sripathik@in.ibm.com>, Oleg Nesterov <oleg@tv-sign.ru>
Subject: Re: [BUG] futex_unlock_pi() hurts my brain and may cause application deadlock
Message-ID: <20070531142455.GA11310@elte.hu>
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* john stultz <johnstul@us.ibm.com> wrote:

> 	So we've been seeing PI mutex deadlocks with a few of our 
> applications using the -rt kernel. After narrowing things down, we 
> were finding that the applications were indirectly calling 
> futex_unlock_pi(), which on occasion would return -EFAULT, which is 
> promptly ignored by glibc. This would cause the application to 
> continue on as if it has unlocked the mutex, until it tried to 
> reacquire it and deadlock.

> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2011,6 +2011,7 @@ pi_faulted:
>  					 attempt);
>  		if (ret)
>  			goto out_unlock;
> +		uval = 0;
>  		goto retry_locked;

this looks good to me. Oleg has posted a few more fixes as well - have 
you tried those too?

	Ingo
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