Re: [PATCH] PM: allow for usage_count > 0 in pm_runtime_get()

Rafael J. Wysocki
2009-11-30T21:06:27Z

On Monday 30 November 2009, Alan Stern wrote:
> This patch (as1308) fixes __pm_runtime_get(). Currently the routine
> will resume a device if the prior usage count was 0. But this isn't
> right; thanks to pm_runtime_get_noresume() the usage count can be
> positive even while the device is suspended.
>
> Now the routine always tries to carry out a resume when called
> synchronously. When called asynchronously, it avoids the overhead of
> an unnecessary spinlock acquisition by doing the resume only if the
> device's state was SUSPENDING or SUSPENDED.
>
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

All three patches applied to suspend-2.6/linux-next. Do you want me to push
them to Linus before 2.6.32, or perhaps the $subject one only?

Rafael

> ---
>
> Index: usb-2.6/drivers/base/power/runtime.c
> ===================================================================
> --- usb-2.6.orig/drivers/base/power/runtime.c
> +++ usb-2.6/drivers/base/power/runtime.c
> @@ -703,16 +703,22 @@ EXPORT_SYMBOL_GPL(pm_request_resume);
> * @dev: Device to handle.
> * @sync: If set and the device is suspended, resume it synchronously.
> *
> - * Increment the usage count of the device and if it was zero previously,
> - * resume it or submit a resume request for it, depending on the value of @sync.
> + * Increment the usage count of the device. If @sync is set, resume the device
> + * and wait for the resume to complete. Otherwise if the device is currently
> + * suspending or suspended, submit a resume request.
> + *
> + * If @sync is clear, the caller is responsible for synchronization.
> */
> int __pm_runtime_get(struct device *dev, bool sync)
> {
> - int retval = 1;
> -
> - if (atomic_add_return(1, &dev->power.usage_count) == 1)
> - retval = sync ? pm_runtime_resume(dev) : pm_request_resume(dev);
> + int retval = 0;
>
> + atomic_inc(&dev->power.usage_count);
> + if (sync)
> + retval = pm_runtime_resume(dev);
> + else if (dev->power.runtime_status == RPM_SUSPENDING ||
> + dev->power.runtime_status == RPM_SUSPENDED)
> + retval = pm_request_resume(dev);
> return retval;
> }
> EXPORT_SYMBOL_GPL(__pm_runtime_get);
> Index: usb-2.6/Documentation/power/runtime_pm.txt
> ===================================================================
> --- usb-2.6.orig/Documentation/power/runtime_pm.txt
> +++ usb-2.6/Documentation/power/runtime_pm.txt
> @@ -276,8 +276,9 @@ drivers/base/power/runtime.c and include
> - increment the device's usage counter
>
> int pm_runtime_get(struct device *dev);
> - - increment the device's usage counter, run pm_request_resume(dev) and
> - return its result
> + - increment the device's usage counter; if the device is currently
> + suspending or suspended then run pm_request_resume(dev) and return its
> + result
>
> int pm_runtime_get_sync(struct device *dev);
> - increment the device's usage counter, run pm_runtime_resume(dev) and