linux-kernel - Re: [RFC/RFT PATCH] PM: sleep: Ignore device driver suspend() callback return values

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Message-ID: <CAJvTdKkqO5D8tZt3L_dbXkXftUOz+zijEjQiWHginn4t_o4gKQ@mail.gmail.com>
Date: Thu, 5 Dec 2024 12:36:22 -0500
From: Len Brown <lenb@...nel.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Alan Stern <stern@...land.harvard.edu>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Saravana Kannan <saravanak@...gle.com>
Subject: Re: [RFC/RFT PATCH] PM: sleep: Ignore device driver suspend()
 callback return values

On Thu, Dec 5, 2024 at 10:33 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:

> ...I also think this looks a bit risky as the current behaviour
> has really been there for a long time. Who knows what depends on this.

If everything were working 100% of the time, no risk would be justified
because no improvement is possible.

But we run over 1,000,000 suspend resume cycles per release in our lab,
and this issue as a category, is the single most common failure.

Worse, there is a huge population of drivers, and we can't possibly test
them all into correctness.  Every release this issue crops when another
driver hiccups in response to some device specific transient issue.

The current implementation is not a viable design.

> A way forward could be to implement the change as an opt-in thing,
> rather than an opt-out. That would allow us to test it and see how it
> plays to potentially change the default behaviour down the road.

The default is the only configuration that matters.

Len Brown, Intel Open Source Technology Center