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?
Yinghai
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