On Friday, November 19, 2010, Alan Stern wrote:
> This patch (as1431b) makes the synchronous runtime-PM interface
> suitable for use in interrupt handlers. Subsystems can call the new
> pm_runtime_irq_safe() function to tell the PM core that a device's
> runtime-PM callbacks should be invoked with interrupts disabled
> (runtime_suspend and runtime_resume callbacks will be invoked with the
> spinlock held as well). This permits the pm_runtime_get_sync() and
> pm_runtime_put_sync() routines to be called from within interrupt
> handlers.
>
> When a device is declared irq-safe in this way, the PM core increments
> the parent's usage count, so the parent will never be runtime
> suspended. This prevents difficult situations in which an irq-safe
> device can't resume because it is forced to wait for its non-irq-safe
> parent.
>
> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> ---
>
> Index: usb-2.6/include/linux/pm.h
> ===================================================================
> --- usb-2.6.orig/include/linux/pm.h
> +++ usb-2.6/include/linux/pm.h
> @@ -486,6 +486,7 @@ struct dev_pm_info {
> unsigned int run_wake:1;
> unsigned int runtime_auto:1;
> unsigned int no_callbacks:1;
> + unsigned int irq_safe:1;
> unsigned int use_autosuspend:1;
> unsigned int timer_autosuspends:1;
> enum rpm_request request;
> Index: usb-2.6/include/linux/pm_runtime.h
> ===================================================================
> --- usb-2.6.orig/include/linux/pm_runtime.h
> +++ usb-2.6/include/linux/pm_runtime.h
> @@ -40,6 +40,7 @@ extern int pm_generic_runtime_idle(struc
> extern int pm_generic_runtime_suspend(struct device *dev);
> extern int pm_generic_runtime_resume(struct device *dev);
> extern void pm_runtime_no_callbacks(struct device *dev);
> +extern void pm_runtime_irq_safe(struct device *dev);
> extern void __pm_runtime_use_autosuspend(struct device *dev, bool use);
> extern void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
> extern unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
> @@ -123,6 +124,7 @@ static inline int pm_generic_runtime_idl
> static inline int pm_generic_runtime_suspend(struct device *dev) { return 0; }
> static inline int pm_generic_runtime_resume(struct device *dev) { return 0; }
> static inline void pm_runtime_no_callbacks(struct device *dev) {}
> +static inline void pm_runtime_irq_safe(struct device *dev) {}
>
> static inline void pm_runtime_mark_last_busy(struct device *dev) {}
> static inline void __pm_runtime_use_autosuspend(struct device *dev,
> 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
> @@ -223,11 +223,19 @@ static int rpm_idle(struct device *dev,
> callback = NULL;
>
> if (callback) {
> - spin_unlock_irq(&dev->power.lock);
> + if (dev->power.irq_safe) {
> + spin_unlock(&dev->power.lock);
>
> - callback(dev);
> + callback(dev);
>
> - spin_lock_irq(&dev->power.lock);
> + spin_lock(&dev->power.lock);
> + } else {
> + spin_unlock_irq(&dev->power.lock);
> +
> + callback(dev);
> +
> + spin_lock_irq(&dev->power.lock);
> + }
> }
I didn't like this change before and I still don't like it. Quite frankly, I'm
not sure I can convince Linus to pull it. :-)
Why don't we simply execute the callback under the spinlock in the
IRQ safe case?
Rafael
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