Re: [BUGFIX 2/9] ACPIPHP: fix device destroying order issue when handling dock notification

[Rafael J. Wysocki]

On Friday, June 14, 2013 12:32:25 AM Jiang Liu wrote:
> Current ACPI glue logic expects that physical devices are destroyed
> before destroying companion ACPI devices, otherwise it will break the
> ACPI unbind logic and cause following warning messages:
> [  185.026073] usb usb5: Oops, 'acpi_handle' corrupt
> [  185.035150] pci 0000:1b:00.0: Oops, 'acpi_handle' corrupt
> [  185.035515] pci 0000:18:02.0: Oops, 'acpi_handle' corrupt
> [  180.013656]  port1: Oops, 'acpi_handle' corrupt
> Please refer to https://bugzilla.kernel.org/attachment.cgi?id=104321
> for full log message.

So my question is, did we have this problem before commit 3b63aaa70e1?

If we did, then when did it start?  Or was it present forever?

> Above warning messages are caused by following scenario:
> 1) acpi_dock_notifier_call() queues a task (T1) onto kacpi_hotplug_wq
> 2) kacpi_hotplug_wq handles T1, which invokes acpi_dock_deferred_cb()
>    ->dock_notify()-> handle_eject_request()->hotplug_dock_devices()
> 3) hotplug_dock_devices() first invokes registered hotplug callbacks to
>    destroy physical devices, then destroys all affected ACPI devices.
>    Everything seems perfect until now. But the acpiphp dock notification
>    handler will queue another task (T2) onto kacpi_hotplug_wq to really
>    destroy affected physical devices.

Would not the solution be to modify it so that it didn't spawn the other
task (T2), but removed the affected physical devices synchronously?

> 4) kacpi_hotplug_wq finishes T1, and all affected ACPI devices have
>    been destroyed.
> 5) kacpi_hotplug_wq handles T2, which destroys all affected physical
>    devices.
> 
> So it breaks ACPI glue logic's expection because ACPI devices are destroyed
> in step 3 and physical devices are destroyed in step 5.
> 
> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
> Reported-by: Alexander E. Patrakov <patrakov@xxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> Hi Bjorn and Rafael,
>      The recursive lock changes haven't been tested yet, need help
> from Alexander for testing.

Well, let's just say I'm not a fan of recursive locks.  Is that unavoidable
here?

Rafael


> ---
>  drivers/acpi/dock.c                | 33 +++++++++++++++++++++++++++------
>  drivers/pci/hotplug/acpiphp_glue.c | 32 ++++++++++++++++++--------------
>  2 files changed, 45 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
> index 02b0563..79c8d9e 100644
> --- a/drivers/acpi/dock.c
> +++ b/drivers/acpi/dock.c
> @@ -65,6 +65,7 @@ struct dock_station {
>  	u32 flags;
>  	spinlock_t dd_lock;
>  	struct mutex hp_lock;
> +	struct task_struct *owner;
>  	struct list_head dependent_devices;
>  	struct list_head hotplug_devices;
>  
> @@ -131,9 +132,13 @@ static void
>  dock_add_hotplug_device(struct dock_station *ds,
>  			struct dock_dependent_device *dd)
>  {
> -	mutex_lock(&ds->hp_lock);
> -	list_add_tail(&dd->hotplug_list, &ds->hotplug_devices);
> -	mutex_unlock(&ds->hp_lock);
> +	if (mutex_is_locked(&ds->hp_lock) && ds->owner == current) {
> +		list_add_tail(&dd->hotplug_list, &ds->hotplug_devices);
> +	} else {
> +		mutex_lock(&ds->hp_lock);
> +		list_add_tail(&dd->hotplug_list, &ds->hotplug_devices);
> +		mutex_unlock(&ds->hp_lock);
> +	}
>  }
>  
>  /**
> @@ -147,9 +152,13 @@ static void
>  dock_del_hotplug_device(struct dock_station *ds,
>  			struct dock_dependent_device *dd)
>  {
> -	mutex_lock(&ds->hp_lock);
> -	list_del(&dd->hotplug_list);
> -	mutex_unlock(&ds->hp_lock);
> +	if (mutex_is_locked(&ds->hp_lock) && ds->owner == current) {
> +		list_del_init(&dd->hotplug_list);
> +	} else {
> +		mutex_lock(&ds->hp_lock);
> +		list_del_init(&dd->hotplug_list);
> +		mutex_unlock(&ds->hp_lock);
> +	}
>  }
>  
>  /**
> @@ -355,7 +364,17 @@ static void hotplug_dock_devices(struct dock_station *ds, u32 event)
>  {
>  	struct dock_dependent_device *dd;
>  
> +	/*
> +	 * There is a deadlock scenario as below:
> +	 *	hotplug_dock_devices()
> +	 *	    mutex_lock(&ds->hp_lock)
> +	 *		dd->ops->handler()
> +	 *		    register_hotplug_dock_device()
> +	 *			mutex_lock(&ds->hp_lock)
> +	 * So we need recursive lock scematics here, do it by ourselves.
> +	 */
>  	mutex_lock(&ds->hp_lock);
> +	ds->owner = current;
>  
>  	/*
>  	 * First call driver specific hotplug functions
> @@ -376,6 +395,8 @@ static void hotplug_dock_devices(struct dock_station *ds, u32 event)
>  		else
>  			dock_create_acpi_device(dd->handle);
>  	}
> +
> +	ds->owner = NULL;
>  	mutex_unlock(&ds->hp_lock);
>  }
>  
> diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> index 716aa93..699b8ca 100644
> --- a/drivers/pci/hotplug/acpiphp_glue.c
> +++ b/drivers/pci/hotplug/acpiphp_glue.c
> @@ -61,6 +61,8 @@ static DEFINE_MUTEX(bridge_mutex);
>  static void handle_hotplug_event_bridge (acpi_handle, u32, void *);
>  static void acpiphp_sanitize_bus(struct pci_bus *bus);
>  static void acpiphp_set_hpp_values(struct pci_bus *bus);
> +static void _handle_hotplug_event_func(acpi_handle handle, u32 type,
> +				       void *context);
>  static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
>  static void free_bridge(struct kref *kref);
>  
> @@ -147,7 +149,7 @@ static int post_dock_fixups(struct notifier_block *nb, unsigned long val,
>  
>  
>  static const struct acpi_dock_ops acpiphp_dock_ops = {
> -	.handler = handle_hotplug_event_func,
> +	.handler = _handle_hotplug_event_func,
>  };
>  
>  /* Check whether the PCI device is managed by native PCIe hotplug driver */
> @@ -1065,22 +1067,13 @@ static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
>  	alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_bridge);
>  }
>  
> -static void _handle_hotplug_event_func(struct work_struct *work)
> +static void _handle_hotplug_event_func(acpi_handle handle, u32 type,
> +				       void *context)
>  {
> -	struct acpiphp_func *func;
> +	struct acpiphp_func *func = context;
>  	char objname[64];
>  	struct acpi_buffer buffer = { .length = sizeof(objname),
>  				      .pointer = objname };
> -	struct acpi_hp_work *hp_work;
> -	acpi_handle handle;
> -	u32 type;
> -
> -	hp_work = container_of(work, struct acpi_hp_work, work);
> -	handle = hp_work->handle;
> -	type = hp_work->type;
> -	func = (struct acpiphp_func *)hp_work->context;
> -
> -	acpi_scan_lock_acquire();
>  
>  	acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
>  
> @@ -1113,7 +1106,18 @@ static void _handle_hotplug_event_func(struct work_struct *work)
>  		warn("notify_handler: unknown event type 0x%x for %s\n", type, objname);
>  		break;
>  	}
> +}
> +
> +static void _handle_hotplug_event_cb(struct work_struct *work)
> +{
> +	struct acpiphp_func *func;
> +	struct acpi_hp_work *hp_work;
>  
> +	hp_work = container_of(work, struct acpi_hp_work, work);
> +	func = (struct acpiphp_func *)hp_work->context;
> +	acpi_scan_lock_acquire();
> +	_handle_hotplug_event_func(hp_work->handle, hp_work->type,
> +				    hp_work->context);
>  	acpi_scan_lock_release();
>  	kfree(hp_work); /* allocated in handle_hotplug_event_func */
>  	put_bridge(func->slot->bridge);
> @@ -1141,7 +1145,7 @@ static void handle_hotplug_event_func(acpi_handle handle, u32 type,
>  	 * don't deadlock on hotplug actions.
>  	 */
>  	get_bridge(func->slot->bridge);
> -	alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_func);
> +	alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_cb);
>  }
>  
>  /*
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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