linux-kernel - Re: PATCH: PM / Runtime: Remove idle notification after failing suspend (was: Re: [linux-pm] [PATCH] PM: add synchronous ...)

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Date:	Sun, 10 Oct 2010 16:18:06 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	linux-pm@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: PATCH: PM / Runtime: Remove idle notification after failing
 suspend (was: Re: [linux-pm] [PATCH] PM: add synchronous ...)

On Sat, 9 Oct 2010, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM / Runtime: Remove idle notification after failing suspend
> 
> If runtime suspend of a device fails returning -EAGAIN or -EBUSY,
> which means that it's safe to try to suspend it again, the PM core
> runs the runtime idle helper function for it.  Unfortunately this may
> lead to problems, for example for PCI devices whose drivers don't
> implement the ->runtime_idle() callback, because in that case the
> PCI bus type's ->runtime_idle() always calls pm_runtime_suspend()
> for the given device.  Thus, if it is automatically called by a
> driver's ->runtime_suspend() returning -EAGAIN or -EBUSY, it will
> cause the suspend to happen again possibly causing a busy loop to
> appear.  To avoid that, remove the idle notification after failing
> runtime suspend of a device altogether and let the callers of
> pm_runtime_suspend() repeat the operation if need be.
> 
> Reported-by: Alan Stern <stern@...land.harvard.edu>
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>

This is fine as far as I'm concerned.

Alan Stern

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