linux-kernel - Re: [RFC PATCH] PM / core: skip suspend next time if resume returns an error

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Message-ID: <20181002080554.GC19677@amd>
Date:   Tue, 2 Oct 2018 10:05:54 +0200
From:   Pavel Machek <pavel@....cz>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     rjw@...ysocki.net, Dilip Kota <dkota@...eaurora.org>,
        dtor@...omium.org, swboyd@...omium.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC PATCH] PM / core: skip suspend next time if resume returns
 an error

Hi!

> In general Linux doesn't behave super great if you get an error while
> executing a device's resume handler.  Nothing will come along later
> and and try again to resume the device (and all devices that depend on
> it), so pretty much you're left with a non-functioning device and
> that's not good.
> 
> However, even though you'll end up with a non-functioning device we
> still don't consider resume failures to be fatal to the system.  We'll
> keep chugging along and just hope that the device that failed to
> resume wasn't too critical.  This establishes the precedent that we
> should at least try our best not to fully bork the system after a
> resume failure.
> 
> I will argue that the best way to keep the system in the best shape is
> to assume that if a resume callback failed that it did as close to
> no-op as possible.  Because of this we should consider the device
> still suspended and shouldn't try to suspend the device again next
> time around.  Today that's not what happens.  AKA if you have a
> device

I don't think there are many guarantees when device resume fail. It
may have done nothing, and it may have resumed the device almost
fully.

I guess the best option would be to refuse system suspend after some
device failed like that.

That leaves user possibility to debug it...

								Pavel-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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