Re: [PATCH] PM: Acquire device locks on suspend

Rafael J. Wysocki
2008-01-06T19:54:55Z

On Sunday, 6 of January 2008, Rafael J. Wysocki wrote:
> On Sunday, 6 of January 2008, Alan Stern wrote:
> > On Sun, 6 Jan 2008, Rafael J. Wysocki wrote:
> >
> > > > If you can figure out a way to disable the warning in device_del() for
> > > > just the one device being unregistered by
> > > > device_pm_destroy_suspended(),
> > >
> > > Something like this, perhaps:
> > >
> > > @@ -905,6 +915,18 @@ void device_del(struct device * dev)
> > > struct device * parent = dev->parent;
> > > struct class_interface *class_intf;
> > >
> > > + if (down_trylock(&dev->sem)) {
> > > + if (pm_sleep_lock()) {
> > > + dev_warn(dev, "Illegal %s during suspend\n",
> > > + __FUNCTION__);
> > > + dump_stack();
> > > + } else {
> > > + pm_sleep_unlock();
> > > + }
> > > + } else {
> > > + up(&dev->sem);
> > > + }
> > > +
> > > if (parent)
> > > klist_del(&dev->knode_parent);
> > > if (MAJOR(dev->devt))
> >
> > Bizarre, but it should work.
>
> OK
>
> Still, shouldn't we fail the removal of the device apart from giving the
> warning?

Actually, having thought about it a bit more, I don't see the point in
preventing the removal of the device from the list in device_pm_remove() if
we allow all of the operations in device_del() preceding it to be performed.

Shouldn't we just take pm_sleep_rwsem in device_del() upfront and block on that
if locked?

Rafael