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

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Message-ID: <CAMuHMdXaaa2t6+sH2egGacVxkAPeTUkAgwdYsOnMnEPnuLdB5Q@mail.gmail.com>
Date:	Thu, 6 Nov 2014 21:38:26 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Ingo Molnar <mingo@...nel.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	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: (bisected) Lock up on sh73a0/kzm9g on cpuidle initialization

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.

I'm using CONFIG_TREE_RCU=y, as this is SMP without PREEMPT.

Anyone with a clue?

Thanks!

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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