[PATCH v1] PM: runtime: Update last_busy in rpm_resume() for active devices

[PATCH v1] PM: runtime: Update last_busy in rpm_resume() for active devices

[Rafael J. Wysocki]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Setting an autosuspend delay for a device can be expected to cause a
runtime suspend of the device after calling, say, pm_runtime_put() to
be deferred, so the time between the last successful attempt to resume
the device and its subsequent suspend is at least equal to the
autosuspend delay.

However, that expectation is only met after the device has been actually
resumed in rpm_resume() by invoking its runtime resume callback.  If the
runtime PM status of the device is already "active" when rpm_resume()
runs for it, the device's last_busy timestamp is not updated which may
allow a subsequent pm_runtime_put() invocation (or similar) to suspend
it right away.

This is arguably inconsistent and confusing, so make rpm_resume() also
update the device's last_busy timestamp when it finds that the device is
already "active" and it is about to return 1 early.

Fixes: 56f487c78015 ("PM / Runtime: Update last_busy in rpm_resume")
Link: https://lore.kernel.org/linux-pm/CAJZ5v0jTX1FgeS9FCV=+V4uacSgLQBVsSPnU27ybgUGg57GUOA@mail.gmail.com/
Reported-by: Brian Norris <briannorris@chromium.org>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/base/power/runtime.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -819,6 +819,12 @@ static int rpm_resume(struct device *dev
 		pm_runtime_deactivate_timer(dev);
 
 	if (dev->power.runtime_status == RPM_ACTIVE) {
+		/*
+		 * The attempt to resume the device means that it is needed for
+		 * something, so update its last_busy timestamp as in the case
+		 * in which it actually resumes below.
+		 */
+		pm_runtime_mark_last_busy(dev);
 		retval = 1;
 		goto out;
 	}

Re: [PATCH v1] PM: runtime: Update last_busy in rpm_resume() for active devices

[Alan Stern]

On Fri, Nov 06, 2026 at 12:31:41PM +0100, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> Setting an autosuspend delay for a device can be expected to cause a
> runtime suspend of the device after calling, say, pm_runtime_put() to
> be deferred, so the time between the last successful attempt to resume
> the device and its subsequent suspend is at least equal to the
> autosuspend delay.
> 
> However, that expectation is only met after the device has been actually
> resumed in rpm_resume() by invoking its runtime resume callback.  If the
> runtime PM status of the device is already "active" when rpm_resume()
> runs for it, the device's last_busy timestamp is not updated which may
> allow a subsequent pm_runtime_put() invocation (or similar) to suspend
> it right away.
> 
> This is arguably inconsistent and confusing, so make rpm_resume() also
> update the device's last_busy timestamp when it finds that the device is
> already "active" and it is about to return 1 early.
> 
> Fixes: 56f487c78015 ("PM / Runtime: Update last_busy in rpm_resume")
> Link: https://lore.kernel.org/linux-pm/CAJZ5v0jTX1FgeS9FCV=+V4uacSgLQBVsSPnU27ybgUGg57GUOA@mail.gmail.com/
> Reported-by: Brian Norris <briannorris@chromium.org>
> Cc: All applicable <stable@vger.kernel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Acked-by: Alan Stern <stern@rowland.harvard.edu>

> ---
>  drivers/base/power/runtime.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -819,6 +819,12 @@ static int rpm_resume(struct device *dev
>  		pm_runtime_deactivate_timer(dev);
>  
>  	if (dev->power.runtime_status == RPM_ACTIVE) {
> +		/*
> +		 * The attempt to resume the device means that it is needed for
> +		 * something, so update its last_busy timestamp as in the case
> +		 * in which it actually resumes below.
> +		 */
> +		pm_runtime_mark_last_busy(dev);
>  		retval = 1;
>  		goto out;
>  	}

Re: [PATCH v1] PM: runtime: Update last_busy in rpm_resume() for active devices

[Brian Norris]

On Fri, Nov 06, 2026 at 12:31:41PM +0100, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> Setting an autosuspend delay for a device can be expected to cause a
> runtime suspend of the device after calling, say, pm_runtime_put() to
> be deferred, so the time between the last successful attempt to resume
> the device and its subsequent suspend is at least equal to the
> autosuspend delay.
> 
> However, that expectation is only met after the device has been actually
> resumed in rpm_resume() by invoking its runtime resume callback.  If the
> runtime PM status of the device is already "active" when rpm_resume()
> runs for it, the device's last_busy timestamp is not updated which may
> allow a subsequent pm_runtime_put() invocation (or similar) to suspend
> it right away.
> 
> This is arguably inconsistent and confusing, so make rpm_resume() also
> update the device's last_busy timestamp when it finds that the device is
> already "active" and it is about to return 1 early.
> 
> Fixes: 56f487c78015 ("PM / Runtime: Update last_busy in rpm_resume")
> Link: https://lore.kernel.org/linux-pm/CAJZ5v0jTX1FgeS9FCV=+V4uacSgLQBVsSPnU27ybgUGg57GUOA@mail.gmail.com/
> Reported-by: Brian Norris <briannorris@chromium.org>

Ha, I suppose you can call it Reported-by, even if it's somewhat of a
tangent IMO :)

> Cc: All applicable <stable@vger.kernel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>