Re: [PATCH v1 1/3] PM: Block enabling of runtime PM during system suspend

[Ulf Hansson]

On Mon, 17 Feb 2025 at 21:20, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> If device_prepare() runs on a device that has never had runtime
> PM enabled so far, it may reasonably assume that runtime PM will
> not be enabled for that device during the system suspend-resume
> cycle currently in progress, but this has never been guaranteed.
>
> To verify this assumption, make device_prepare() arrange for
> triggering a device warning accompanied by a call trace dump if
> runtime PM is enabled for such a device after it has returned.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
>  drivers/base/power/main.c    |    9 +++++++++
>  drivers/base/power/runtime.c |   24 ++++++++++++++++++++++++
>  include/linux/pm.h           |    1 +
>  include/linux/pm_runtime.h   |    6 +++++-
>  4 files changed, 39 insertions(+), 1 deletion(-)
>
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1109,6 +1109,8 @@
>         device_unlock(dev);
>
>  out:
> +       /* If enabling runtime PM for the device is blocked, unblock it. */
> +       pm_runtime_unblock(dev);
>         pm_runtime_put(dev);
>  }
>
> @@ -1815,6 +1817,13 @@
>          * it again during the complete phase.
>          */
>         pm_runtime_get_noresume(dev);
> +       /*
> +        * If runtime PM is disabled for the device at this point and it has
> +        * never been enabled so far, it should not be enabled until this system
> +        * suspend-resume cycle is complete, so prepare to trigger a warning on
> +        * subsequent attempts to enable it.
> +        */
> +       pm_runtime_block_if_disabled(dev);
>
>         if (dev->power.syscore)
>                 return 0;
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1460,6 +1460,26 @@
>  }
>  EXPORT_SYMBOL_GPL(pm_runtime_barrier);
>
> +void pm_runtime_block_if_disabled(struct device *dev)
> +{
> +       spin_lock_irq(&dev->power.lock);
> +
> +       if (dev->power.disable_depth && dev->power.last_status == RPM_INVALID)
> +               dev->power.last_status = RPM_BLOCKED;
> +
> +       spin_unlock_irq(&dev->power.lock);
> +}
> +
> +void pm_runtime_unblock(struct device *dev)
> +{
> +       spin_lock_irq(&dev->power.lock);
> +
> +       if (dev->power.last_status == RPM_BLOCKED)
> +               dev->power.last_status = RPM_INVALID;
> +
> +       spin_unlock_irq(&dev->power.lock);
> +}
> +
>  void __pm_runtime_disable(struct device *dev, bool check_resume)
>  {
>         spin_lock_irq(&dev->power.lock);
> @@ -1518,6 +1538,10 @@
>         if (--dev->power.disable_depth > 0)
>                 goto out;
>
> +       if (dev->power.last_status == RPM_BLOCKED) {
> +               dev_warn(dev, "Attempt to enabled runtime PM when it is blocked\n");

/s/enabled/enable

> +               dump_stack();
> +       }
>         dev->power.last_status = RPM_INVALID;
>         dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
>
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -597,6 +597,7 @@
>         RPM_RESUMING,
>         RPM_SUSPENDED,
>         RPM_SUSPENDING,
> +       RPM_BLOCKED,
>  };
>
>  /*
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -77,8 +77,10 @@
>  extern int pm_schedule_suspend(struct device *dev, unsigned int delay);
>  extern int __pm_runtime_set_status(struct device *dev, unsigned int status);
>  extern int pm_runtime_barrier(struct device *dev);
> +extern void pm_runtime_block_if_disabled(struct device *dev);
> +extern void pm_runtime_unblock(struct device *dev);
>  extern void pm_runtime_enable(struct device *dev);
> -extern void __pm_runtime_disable(struct device *dev, bool check_resume);
> +extern void __pm_runtime_disable(struct device *dev, bool regular);

This looks unrelated to the $subject patch.

>  extern void pm_runtime_allow(struct device *dev);
>  extern void pm_runtime_forbid(struct device *dev);
>  extern void pm_runtime_no_callbacks(struct device *dev);
> @@ -271,6 +273,8 @@
>  static inline int __pm_runtime_set_status(struct device *dev,
>                                             unsigned int status) { return 0; }
>  static inline int pm_runtime_barrier(struct device *dev) { return 0; }
> +static inline void pm_runtime_block_if_disabled(struct device *dev) {}
> +static inline void pm_runtime_unblock(struct device *dev) {}
>  static inline void pm_runtime_enable(struct device *dev) {}
>  static inline void __pm_runtime_disable(struct device *dev, bool c) {}
>  static inline void pm_runtime_allow(struct device *dev) {}
>
>
>

With the minor things above fixed, feel free to add:

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

Kind regards
Uffe