Re: [PATCH] PM / core: Clear the direct_complete flag on errors

[Ulf Hansson]

On 4 October 2018 at 11:08, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> If __device_suspend() returns early on an error or pending wakeup
> and the power.direct_complete flag has been set for the device
> already, the subsequent device_resume() will be confused by it
> and it will call pm_runtime_enable() incorrectly, as runtime PM
> has not been disabled for the device by __device_suspend().

I think it would be fair to mention that is related to the async
suspend path, in dpm_suspend().

>
> To avoid that, clear power.direct_complete if __device_suspend()
> is not going to disable runtime PM for the device before returning.

Overall, by looking at the behavior in dpm_suspend() of async
suspended devices, it does look a bit fragile to me.

My worries is that we put asynced suspended devices in the
dpm_suspended_list, no matter if the device was successfully suspended
or not. This differs from the no-async path.

In the long run, maybe we should change that instead?

>
> Fixes: aae4518b3124 (PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily)
> Reported-by: Al Cooper <alcooperx@xxxxxxxxx>
> Cc: 3.16+ <stable@xxxxxxxxxxxxxxx> # 3.16+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Reviewed-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Kind regards
Uffe

> ---
>  drivers/base/power/main.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -1713,8 +1713,10 @@ static int __device_suspend(struct devic
>
>         dpm_wait_for_subordinate(dev, async);
>
> -       if (async_error)
> +       if (async_error) {
> +               dev->power.direct_complete = false;
>                 goto Complete;
> +       }
>
>         /*
>          * If a device configured to wake up the system from sleep states
> @@ -1726,6 +1728,7 @@ static int __device_suspend(struct devic
>                 pm_wakeup_event(dev, 0);
>
>         if (pm_wakeup_pending()) {
> +               dev->power.direct_complete = false;
>                 async_error = -EBUSY;
>                 goto Complete;
>         }
>