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

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Date:   Thu, 22 Sep 2022 21:33:47 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Alan Stern <stern@...land.harvard.edu>
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>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] PM: runtime: Return -EINPROGRESS from rpm_resume() in the
 RPM_NOWAIT case

On Thu, Sep 22, 2022 at 9:32 PM Alan Stern <stern@...land.harvard.edu> wrote:
>
> On Thu, Sep 22, 2022 at 08:04:40PM +0200, Rafael J. Wysocki 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.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/base/power/runtime.c |    7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > Index: linux-pm/drivers/base/power/runtime.c
> > ===================================================================
> > --- linux-pm.orig/drivers/base/power/runtime.c
> > +++ linux-pm/drivers/base/power/runtime.c
> > @@ -792,10 +792,13 @@ static int rpm_resume(struct device *dev
> >               DEFINE_WAIT(wait);
> >
> >               if (rpmflags & (RPM_ASYNC | RPM_NOWAIT)) {
>
> Hmmm, and what if a caller sets both of these flags?  I guess in that
> case he gets what he deserves.

Exactly.

> > -                     if (dev->power.runtime_status == RPM_SUSPENDING)
> > +                     if (dev->power.runtime_status == RPM_SUSPENDING) {
> >                               dev->power.deferred_resume = true;
> > -                     else
> > +                             if (rpmflags & RPM_NOWAIT)
> > +                                     retval = -EINPROGRESS;
> > +                     } else {
> >                               retval = -EINPROGRESS;
> > +                     }
> >                       goto out;
> >               }
>
> Acked-by: Alan Stern <stern@...land.harvard.edu>

Thanks!