linux-kernel - Re: [PATCH] PM: runtime: Return -EINPROGRESS from rpm_resume() in the RPM

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Date:   Mon, 26 Sep 2022 11:49:30 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] PM: runtime: Return -EINPROGRESS from rpm_resume() in the
 RPM_NOWAIT case

On Fri, 23 Sept 2022 at 17:53, Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Fri, Sep 23, 2022 at 3:26 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >
> > On Thu, 22 Sept 2022 at 20:04, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > >
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >
> > > The prospective callers of rpm_resume() passing RPM_NOWAIT to it may
> > > be confused when it returns 0 without actually resuming the device
> > > which may happen if the device is suspending at the given time and it
> > > will only resume when the suspend in progress has completed.  To avoid
> > > that confusion, return -EINPROGRESS from rpm_resume() in that case.
> > >
> > > Since none of the current callers passing RPM_NOWAIT to rpm_resume()
> > > check its return value, this change has no functional impact.
> >
> > Sounds like there are additional improvements that can be made around
> > this, right?
>
> This allows RPM_NOWAIT to be used in places where the caller doesn't
> want to wait, because it might deadlock or similar, but they still
> need to know whether or not the device can be accessed safely.
>
> Or do you mean something else?

Nope, I was mostly wondering if you are planning to make those
improvements too. Sooner or later.

[...]

Kind regards
Uffe