linux-kernel - Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code

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Message-ID: <CAMuHMdVPs4M+4wvNHWCFKe0rxJfDPF-K+zCFgRm-MdRUY4D-Eg@mail.gmail.com>
Date:	Tue, 23 Jun 2015 09:16:21 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Kevin Hilman <khilman@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Magnus Damm <damm@...nsource.se>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code

Hi Rafael,

On Tue, Jun 23, 2015 at 1:41 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Monday, June 22, 2015 09:31:22 AM Geert Uytterhoeven wrote:
>> If pm_genpd_{add,remove}_device() keeps on failing with -EAGAIN, we end
>> up with an infinite loop in genpd_dev_pm_{at,de}tach().
>>
>> This may happen due to a genpd.prepared_count imbalance.  This is a bug
>> elsewhere, but it will result in a system lock up, possibly during
>> reboot of an otherwise functioning system.
>>
>> To avoid this, put a limit on the maximum number of loop iterations,
>> including a simple back-off mechanism.  If the limit is reached, the
>> operation will just fail.  An error message is already printed.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> This was too late for my first 4.2 pull request, but I may push it in the
> second half of the merge window.  Does it depend on anything?

Not that I'm aware of.

It applies fine on v4.1 or next-20150622.

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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