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SubjectRe: [RFC][PATCH 2/3] PM: Asynchronous suspend of devices
Date
On Friday 14 August 2009, Pavel Machek wrote:
> > @@ -659,26 +674,61 @@ static pm_message_t resume_event(pm_mess
> > }
> >
> > /**
> > - * device_suspend_noirq - Shut down one device (late suspend).
> > - * @dev: Device.
> > - * @state: PM transition of the system being carried out.
> > + * __device_suspend_noirq - Execute a "late" suspend callback for given device.
> > + * @dev: Device to suspend.
> > + * @state: PM transition of the system being carried out.
>
> > *
> > - * This is called with interrupts off and only a single CPU running.
>
> that still looks like useful comment... why delete it?

Because it's not valid any more.

> > + * The driver of the device won't receive interrupts while this function is
> > + * being executed.
> > */
> > @@ -696,13 +746,19 @@ int dpm_suspend_noirq(pm_message_t state
> > suspend_device_irqs();
> > mutex_lock(&dpm_list_mtx);
> > list_for_each_entry_reverse(dev, &dpm_list, power.entry) {
> > + dev->power.status = DPM_OFF_IRQ;
> > error = device_suspend_noirq(dev, state);
> > if (error) {
> > pm_dev_err(dev, state, " late", error);
> > + dev->power.status = DPM_OFF;
> > + break;
> > + }
> > + if (async_error) {
> > + error = async_error;
> > break;
>
> async_error is 'interesting'. How does locking work in noirq case?

It's racy, a little bit. :-)

If two async drivers return errors exactly at the same time, one of them will
win the race, but it doesn't really matter which one wins as long as
async_error is different from zero as a result. And it will be, since it's
an 'int' and the integrity of these is guaranteed.

Thanks,
Rafael


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