On Friday, July 21, 2017 06:45:03 PM Andy Shevchenko wrote:
> On Fri, Jul 21, 2017 at 3:42 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> > The acpi_pci_propagate_wakeup() routine is there to handle cases in
> > which PCI bridges (or PCIe ports) are expected to signal wakeup
> > for devices below them, but currently it doesn't do that correctly.
> >
> > The problem is that acpi_pci_propagate_wakeup() uses
> > acpi_pm_set_device_wakeup() for bridges and if that routine is
> > called for multiple times to disable wakeup for the same device,
> > it will disable it on the first invocation and the next calls
> > will have no effect (it works analogously when called to enable
> > wakeup, but that is not a problem).
> >
> > Now, say acpi_pci_propagate_wakeup() has been called for two
> > different devices under the same bridge and it has called
> > acpi_pm_set_device_wakeup() for that bridge each time. The
> > bridge is now enabled to generate wakeup signals. Next,
> > suppose that one of the devices below it resumes and
> > acpi_pci_propagate_wakeup() is called to disable wakeup for that
> > device. It will then call acpi_pm_set_device_wakeup() for the bridge
> > and that will effectively disable remote wakeup for all devices under
> > it even though some of them may still be suspended and remote wakeup
> > may be expected to work for them.
> >
> > To address this (arguably theoretical) issue, allow
> > wakeup.enable_count under struct acpi_device to grow beyond 1 in
> > certain situations. In particular, allow that to happen in
> > acpi_pci_propagate_wakeup() when wakeup is enabled or disabled
> > for PCI bridges, so that wakeup is actually disabled for the
> > bridge when all devices under it resume and not when just one
> > of them does that.
>
> > - if (wakeup->enable_count > 0)
> > - goto out;
> > + if (wakeup->enable_count > 0) {
> > + if (wakeup->enable_count < max_count)
> > + goto inc;
> > + else
> > + goto out;
> > + }
>
> Wouldn't be simpler
I'm not really sure what you mean.
In general, ->
> if (wakeup->enable_count >= max_count)
> goto out;
-> this is unlikely and ->>
> if (wakeup->enable_count > 0)
> goto inc;
->> this isn't.
Why would checking an unlikely condition before a likely one covering it
ever be better?
> If max_count can be <= 0,
No, it can't be.
Thanks,
Rafael
