linux-kernel - Re: RCU lockup in the SMP idle thread, help...

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Message-ID: <CACRpkdaufGjsEtkjQFY9oDvmtM7xnEiFweLfOGuX+WRf0Vbb5A@mail.gmail.com>
Date:	Thu, 20 Sep 2012 11:07:37 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	John Stultz <john.stultz@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: RCU lockup in the SMP idle thread, help...

On Thu, Sep 20, 2012 at 2:03 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:

> In the meantime, a crude fallback is for the CPU that detected the stall
> to trace the stack of the task running on the other CPU.  See below for
> a crude (and untested) patch.

OK now I get this:

 INFO: rcu_preempt detected stalls on CPUs/tasks: { 0} (detected by 1,
t=29508 jiffies)
Task dump for CPU 0:
swapper/0       R running      0     0      0 0x00000000
[<c02da614>] (__schedule+0x238/0x52c) from [<c000f238>] (default_idle+0x28/0x30)
[<c000f238>] (default_idle+0x28/0x30) from [<ffffffff>] (0xffffffff)
INFO: rcu_preempt detected stalls on CPUs/tasks: { 0} (detected by 1,
t=29851 jiffies)
Task dump for CPU 0:
swapper/0       R running      0     0      0 0x00000000
[<c02da614>] (__schedule+0x238/0x52c) from [<c000f238>] (default_idle+0x28/0x30)
[<c000f238>] (default_idle+0x28/0x30) from [<ffffffff>] (0xffffffff)

So the swapper thread is the culprit?
Hm, I'm not very smart with this no...

Yours,
Linus Walleij
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