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

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Date:   Thu, 22 Sep 2022 15:32:11 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     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 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.

> -			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>