linux-kernel - Re: RCU stall in af_unix.c, should use spin_lock

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Message-ID: <20141021121304.076d5acd@free-electrons.com>
Date:	Tue, 21 Oct 2014 12:13:04 +0200
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alexandre FOURNIER <alexandre.fournier@...p-e.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Marcin Wojtas <mw@...ihalf.com>,
	Gregory Clément 
	<gregory.clement@...e-electrons.com>
Subject: Re: RCU stall in af_unix.c, should use spin_lock_irqsave?

Dear Hannes Frederic Sowa,

On Tue, 21 Oct 2014 12:08:52 +0200, Hannes Frederic Sowa wrote:
> On Di, 2014-10-21 at 10:03 +0200, Thomas Petazzoni wrote:
> > So, the question is: is this patch the correct solution (but then other
> > usage of spin_lock in af_unix.c might also need fixing) ? Or is the
> > network driver at fault?
> 
> It feels like a false positive. Do you see one core spinning tightly on
> a lock? Does the system get unusable?

Interrupts are still enabled (for example, sysrq are still working),
but scheduling no longer takes place (all processes are blocked).

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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