linux-kernel - Re: [PATCH] ACPI: PM: Fix device wakeup power reference counting error

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Date:   Fri, 5 Nov 2021 15:39:13 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH] ACPI: PM: Fix device wakeup power reference counting error

On Thu, Nov 4, 2021 at 10:54 PM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> On Thursday, November 4, 2021 6:21:51 PM CET Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Fix a device wakeup power reference counting error introduced by
> > commit a2d7b2e004af ("ACPI: PM: Fix sharing of wakeup power
> > resources").
> >
> > Fixes: a2d7b2e004af ("ACPI: PM: Fix sharing of wakeup power resources")
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/acpi/power.c |    4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > Index: linux-pm/drivers/acpi/power.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/power.c
> > +++ linux-pm/drivers/acpi/power.c
> > @@ -757,10 +757,8 @@ int acpi_disable_wakeup_device_power(str
> >
> >       mutex_lock(&acpi_device_lock);
> >
> > -     if (dev->wakeup.prepare_count > 1) {
> > +     if (dev->wakeup.prepare_count >= 1)
> >               dev->wakeup.prepare_count--;
> > -             goto out;
> > -     }
> >
> >       /* Do nothing if wakeup power has not been enabled for this device. */
> >       if (!dev->wakeup.prepare_count)
>
> This is still not good.  It should be something like the patch below, but I
> need to test that one.

Tested now, so applying as 5.16-rc material.

> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH v2] ACPI: PM: Fix device wakeup power reference counting error
>
> Fix a device wakeup power reference counting error introduced by
> commit a2d7b2e004af ("ACPI: PM: Fix sharing of wakeup power
> resources").
>
> Fixes: a2d7b2e004af ("ACPI: PM: Fix sharing of wakeup power resources")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> -> v2: Actually disable wakeup power when the reference count becomes zero.
>
> ---
>  drivers/acpi/power.c |    8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> Index: linux-pm/drivers/acpi/power.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/power.c
> +++ linux-pm/drivers/acpi/power.c
> @@ -757,13 +757,11 @@ int acpi_disable_wakeup_device_power(str
>
>         mutex_lock(&acpi_device_lock);
>
> -       if (dev->wakeup.prepare_count > 1) {
> -               dev->wakeup.prepare_count--;
> +       /* Do nothing if wakeup power has not been enabled for this device. */
> +       if (dev->wakeup.prepare_count <= 0)
>                 goto out;
> -       }
>
> -       /* Do nothing if wakeup power has not been enabled for this device. */
> -       if (!dev->wakeup.prepare_count)
> +       if (--dev->wakeup.prepare_count > 0)
>                 goto out;
>
>         err = acpi_device_sleep_wake(dev, 0, 0, 0);
>
>
>
>