From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Deadlocks due to per-process plugging
Date: Sun, 15 Jul 2012 10:59:34 +0200 (CEST)
Message-ID: <alpine.LFD.2.02.1207151057010.32033@ionos>
References: <20120711133735.GA8122@quack.suse.cz> <x49ehoii8ps.fsf@segfault.boston.devel.redhat.com> <20120711201601.GB9779@quack.suse.cz> <alpine.LFD.2.02.1207121552111.32033@ionos> <20120713123318.GB20361@quack.suse.cz> <alpine.LFD.2.02.1207131444490.32033@ionos>
 <20120713144622.GB28715@quack.suse.cz>
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Cc: Jeff Moyer <jmoyer@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
	Jens Axboe <jaxboe@fusionio.com>, mgalbraith@suse.com
To: Jan Kara <jack@suse.cz>
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On Fri, 13 Jul 2012, Jan Kara wrote:
> On Fri 13-07-12 16:25:05, Thomas Gleixner wrote:
> > So the patch below should allow the unplug to take place when blocked
> > on mutexes etc.
>   Thanks for the patch! Mike will give it some testing.

I just found out that this patch will explode nicely when the unplug
code runs into a contended lock. Then we try to block on that lock and
make the rtmutex code unhappy as we are already blocked on something
else.

So no, it's not a solution to the problem. Sigh.

Can you figure out on which lock the stuck thread which did not unplug
due to tsk_is_pi_blocked was blocked?

Thanks,

	tglx