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

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Message-ID: <CACRpkdatjfk_eUof5G4fwa-Qf8SoF_NvSUJQAZ7U8yjcSYFuTA@mail.gmail.com>
Date:	Fri, 14 Sep 2012 09:27:32 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	paulmck@...ux.vnet.ibm.com, John Stultz <john.stultz@...aro.org>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: RCU lockup in the SMP idle thread, help...

On Thu, Sep 13, 2012 at 6:58 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Thu, Sep 13, 2012 at 09:49:14AM -0700, John Stultz wrote:
>> I saw this once as well testing the fix to Daniel's deep idle hang
>> issue (also on 32 bit).

John, what system was this? If it's not Snowball/ux500 we can atleast
conclude that
it's a generic bug, not machine-specific...

>> Really briefly looking at the code in rcutree.c, I'm curious if
>> we're hitting a false positive on the 5 minute jiffies overflow?
>
> Hmmm...  Might be.  Does the patch below help?

Sorry, nope, I get this:

root@ME:/
root@ME:/ INFO: rcu_preempt detected stalls on CPUs/tasks: { 0}
(detected by 1, t=29545 jiffies)
[<c0014710>] (unwind_backtrace+0x0/0xf8) from [<c00686fc>]
(rcu_check_callbacks+0x6e0/0x76c)
[<c00686fc>] (rcu_check_callbacks+0x6e0/0x76c) from [<c0029cbc>]
(update_process_times+0x38/0x4c)
[<c0029cbc>] (update_process_times+0x38/0x4c) from [<c0055088>]
(tick_sched_timer+0x80/0xe4)
[<c0055088>] (tick_sched_timer+0x80/0xe4) from [<c003c120>]
(__run_hrtimer.isra.18+0x44/0xd0)
[<c003c120>] (__run_hrtimer.isra.18+0x44/0xd0) from [<c003cae0>]
(hrtimer_interrupt+0x118/0x2b4)
[<c003cae0>] (hrtimer_interrupt+0x118/0x2b4) from [<c0013658>]
(twd_handler+0x30/0x44)
[<c0013658>] (twd_handler+0x30/0x44) from [<c00638c8>]
(handle_percpu_devid_irq+0x80/0xa0)
[<c00638c8>] (handle_percpu_devid_irq+0x80/0xa0) from [<c00603b8>]
(generic_handle_irq+0x20/0x30)
[<c00603b8>] (generic_handle_irq+0x20/0x30) from [<c000ef58>]
(handle_IRQ+0x4c/0xac)
[<c000ef58>] (handle_IRQ+0x4c/0xac) from [<c00084bc>] (gic_handle_irq+0x24/0x58)
[<c00084bc>] (gic_handle_irq+0x24/0x58) from [<c000dc80>] (__irq_svc+0x40/0x70)
Exception stack(0xcf865f88 to 0xcf865fd0)
5f80:                   00000020 c05c0a20 00000001 00000000 cf864000 cf864000
5fa0: c05dfe48 c02de0bc c05c3e90 412fc091 cf864000 00000000 01000000 cf865fd0
5fc0: c000f234 c000f238 60000013 ffffffff
[<c000dc80>] (__irq_svc+0x40/0x70) from [<c000f238>] (default_idle+0x28/0x30)
[<c000f238>] (default_idle+0x28/0x30) from [<c000f438>] (cpu_idle+0x98/0xe4)
[<c000f438>] (cpu_idle+0x98/0xe4) from [<002d3094>] (0x2d3094)
INFO: rcu_preempt detected stalls on CPUs/tasks: { 0} (detected by 1,
t=30029 jiffies)
[<c0014710>] (unwind_backtrace+0x0/0xf8) from [<c00686fc>]
(rcu_check_callbacks+0x6e0/0x76c)
[<c00686fc>] (rcu_check_callbacks+0x6e0/0x76c) from [<c0029cbc>]
(update_process_times+0x38/0x4c)
[<c0029cbc>] (update_process_times+0x38/0x4c) from [<c0055088>]
(tick_sched_timer+0x80/0xe4)
[<c0055088>] (tick_sched_timer+0x80/0xe4) from [<c003c120>]
(__run_hrtimer.isra.18+0x44/0xd0)
[<c003c120>] (__run_hrtimer.isra.18+0x44/0xd0) from [<c003cae0>]
(hrtimer_interrupt+0x118/0x2b4)
[<c003cae0>] (hrtimer_interrupt+0x118/0x2b4) from [<c0013658>]
(twd_handler+0x30/0x44)
[<c0013658>] (twd_handler+0x30/0x44) from [<c00638c8>]
(handle_percpu_devid_irq+0x80/0xa0)
[<c00638c8>] (handle_percpu_devid_irq+0x80/0xa0) from [<c00603b8>]
(generic_handle_irq+0x20/0x30)
[<c00603b8>] (generic_handle_irq+0x20/0x30) from [<c000ef58>]
(handle_IRQ+0x4c/0xac)
[<c000ef58>] (handle_IRQ+0x4c/0xac) from [<c00084bc>] (gic_handle_irq+0x24/0x58)
[<c00084bc>] (gic_handle_irq+0x24/0x58) from [<c000dc80>] (__irq_svc+0x40/0x70)
Exception stack(0xcf865f88 to 0xcf865fd0)
5f80:                   00000020 c05c0a20 00000001 00000000 cf864000 cf864000
5fa0: c05dfe48 c02de0bc c05c3e90 412fc091 cf864000 00000000 01000000 cf865fd0
5fc0: c000f234 c000f238 60000013 ffffffff
[<c000dc80>] (__irq_svc+0x40/0x70) from [<c000f238>] (default_idle+0x28/0x30)
[<c000f238>] (default_idle+0x28/0x30) from [<c000f438>] (cpu_idle+0x98/0xe4)
[<c000f438>] (cpu_idle+0x98/0xe4) from [<002d3094>] (0x2d3094)

I'm all confused ..

Yours,
Linus Walleij
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