Re: [linux-pm] [PATCH] PM: runtime PM + idle: allow usage when interrupts are disabled

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday, August 10, 2010, Kevin Hilman wrote:
> When using runtime PM in combination with CPUidle, the runtime PM
> transtions of some devices may be triggered during the idle path.
> Late in the idle sequence, interrupts will likely be disabled when
> runtime PM for these devices is initiated.
> 
> Currently, the runtime PM core assumes methods are called with
> interrupts enabled.  However, if it is called with interrupts
> disabled, the internal locking unconditionally enables interrupts, for
> example:
> 
> pm_runtime_put_sync()

Please don't use that from interrupt context.  There's pm_runtime_put()
exactly for this purpose that puts the _idle() call into a workqueue.

>     __pm_runtime_put()
>         pm_runtime_idle()
>             spin_lock_irq()
>             __pm_runtime_idle()
>                 spin_unlock_irq()   <--- interrupts unconditionally enabled

That's because __pm_runtime_idle() has to be called from process context.

>                 dev->bus->pm->runtime_idle()
>                 spin_lock_irq()
>              spin_unlock_irq()

Thanks,
Rafael