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

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Message-ID: <5913118.ZpKlm0JFgd@vostro.rjw.lan>
Date:	Tue, 23 Jun 2015 01:41:04 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Geert Uytterhoeven <geert+renesas@...der.be>
Cc:	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@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code

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?

Rafael

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