On Saturday, June 22, 2013 05:22:20 PM Yinghai Lu wrote:
> On Sat, Jun 22, 2013 at 2:25 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > To resolve that deadlock use the observation that
> > unregister_hotplug_dock_device() won't need to acquire hp_lock
> > if PCI bridges the devices on the dock station depend on are
> > prevented from being removed prematurely while the first loop in
> > hotplug_dock_devices() is in progress.
> >
> > To make that possible, introduce a mechanism by which the callers of
> > register_hotplug_dock_device() can provide "init" and "release"
> > routines that will be executed, respectively, after the addition
> > and removal of the physical device object associated with the
> > given ACPI device handle. Make acpiphp use two new functions,
> > acpiphp_dock_init() and acpiphp_dock_release(), respectively,
> > calling get_bridge() and put_bridge() on the PCI bridge holding the
> > given device, respectively, for this purpose.
> >
> > In addition to that, remove the dock station's list of
> > "hotplug devices" and make the dock code always walk the whole list
> > of "dependent devices" instead in such a way that the loops in
> > hotplug_dock_devices() and dock_event() (replacing the loops over
> > "hotplug devices") will take references to the list entries that
> > register_hotplug_dock_device() has been called for. That prevents
> > the "release" routines associated with those entries from being
> > called while the given entry is being processed and for PCI
> > devices this means that their bridges won't be removed (by a
> > concurrent thread) while hotplug_event_func() handling them is
> > being executed.
> ..
> > -static void
> > -dock_del_hotplug_device(struct dock_station *ds,
> > - struct dock_dependent_device *dd)
> > +static void dock_release_hotplug(struct dock_dependent_device *dd)
> > {
> > - mutex_lock(&ds->hp_lock);
> > - list_del(&dd->hotplug_list);
> > - mutex_unlock(&ds->hp_lock);
> > + void (*release)(void *) = NULL;
> > + void *context = NULL;
> > +
> > + mutex_lock(&hotplug_lock);
> > +
> > + if (dd->hp_context && !--dd->hp_refcount) {
> > + dd->hp_ops = NULL;
> > + context = dd->hp_context;
> > + dd->hp_context = NULL;
> > + release = dd->hp_release;
> > + dd->hp_release = NULL;
> > + }
> > +
> > + if (release && context)
> > + release(context);
> > +
> > + mutex_unlock(&hotplug_lock);
> > +}
> > +
> > +static void dock_hotplug_event(struct dock_dependent_device *dd, u32 event,
> > + bool uevent)
> > +{
> > + acpi_notify_handler cb = NULL;
> > + bool run = false;
> > +
> > + mutex_lock(&hotplug_lock);
> > +
> > + if (dd->hp_context) {
> > + run = true;
> > + dd->hp_refcount++;
> > + if (dd->hp_ops)
> > + cb = uevent ? dd->hp_ops->uevent : dd->hp_ops->handler;
> > + }
> > +
> > + mutex_unlock(&hotplug_lock);
> > +
> > + if (!run)
> > + return;
> > +
> > + if (cb)
> > + cb(dd->handle, event, dd->hp_context);
> > +
> > + dock_release_hotplug(dd);
>
> during DOCKING, dock_release_hotplug get called too?
Yes, we need to drop down the refcount we've just bumped up.
Thanks,
Rafael
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