linux-kernel - Re: (bisected) Lock up on sh73a0/kzm9g on cpuidle initialization

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Date:	Fri, 7 Nov 2014 08:59:25 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: (bisected) Lock up on sh73a0/kzm9g on cpuidle initialization

Hi Daniel,

On Thu, Nov 6, 2014 at 10:02 PM, Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
> On 11/06/2014 09:38 PM, Geert Uytterhoeven wrote:
>> When CONFIG_CPU_IDLE=y, the kernel locks up during cpuidle initialization
>> on Renesas sh73a0/kzm9g-reference, which has a dual-core Cortex-A9.
>>
>> Last message is:
>>
>>      DMA: preallocated 256 KiB pool for atomic coherent allocations
>>
>> After this it's supposed to print:
>>
>>      cpuidle: using governor ladder
>>      cpuidle: using governor menu
>>
>> I've bisected this to commit 442bf3aaf55a91ebfec71da46a4ee10a3c905bcc
>> ("sched: Let the scheduler see CPU idle states").
>>
>> Reverting that commit, and commit 83a0a96a5f26d974580fd7251043ff70c8f1823d
>> ("sched/fair: Leverage the idle state info when choosing the "idlest"
>> cpu") which
>> depends on it, fixes the problem.
>>
>> I saw the discussion "lockdep splat in CPU hotplug", so I enabled lockdep
>> debugging, but didn't see a lockdep splat.
>
> Did you try the fix attached ?
>
> https://lkml.org/lkml/2014/10/22/722

Thanks, I didn't try that.

However, this patch seems to be in v3.18-rc3, so I'm already using it.
Hence it doesn't fix the problem for me.

On another board, with a dual Cortex-A15, the problem doesn't show up.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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