On 06/14/2013 10:12 PM, Rafael J. Wysocki wrote:
> On Friday, June 14, 2013 09:57:15 PM Jiang Liu wrote:
>> On 06/14/2013 08:23 PM, Rafael J. Wysocki wrote:
>>> On Thursday, June 13, 2013 09:59:44 PM Rafael J. Wysocki wrote:
>>>> 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 <[email protected]>
>>>>> Reported-by: Alexander E. Patrakov <[email protected]>
>>>>> Cc: Bjorn Helgaas <[email protected]>
>>>>> Cc: Yinghai Lu <[email protected]>
>>>>> Cc: "Rafael J. Wysocki" <[email protected]>
>>>>> Cc: [email protected]
>>>>> Cc: [email protected]
>>>>> Cc: [email protected]
>>>>> ---
>>>>> 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?
>>>
>>> What about the appended patch (on top of [1/9], untested)?
>>>
>>> Rafael
>> It should have similar effect as patch 2/9, and it will encounter the
>> same deadlock scenario as 2/9 too.
>
> And why exactly?
>
> I'm looking at acpiphp_disable_slot() and I'm not seeing where the
> problematic lock is taken. Similarly for power_off_slot().
>
> It should take the ACPI scan lock, but that's a different matter.
>
> Thanks,
> Rafael
The deadlock scenario is the same:
hotplug_dock_devices()
mutex_lock(&ds->hp_lock)
dd->ops->handler()
destroy pci bus
unregister_hotplug_dock_device()
mutex_lock(&ds->hp_lock)
>
>
>>> ---
>>> drivers/pci/hotplug/acpiphp_glue.c | 13 ++++++++++++-
>>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>>
>>> Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
>>> ===================================================================
>>> --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
>>> +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
>>> @@ -145,9 +145,20 @@ static int post_dock_fixups(struct notif
>>> return NOTIFY_OK;
>>> }
>>>
>>> +static void handle_dock_event_func(acpi_handle handle, u32 event, void
>>> *context)
>>> +{
>>> + if (event == ACPI_NOTIFY_EJECT_REQUEST) {
>>> + struct acpiphp_func *func = context;
>>> +
>>> + if (!acpiphp_disable_slot(func->slot))
>>> + acpiphp_eject_slot(func->slot);
>>> + } else {
>>> + handle_hotplug_event_func(handle, event, context);
>>> + }
>>> +}
>>>
>>> static const struct acpi_dock_ops acpiphp_dock_ops = {
>>> - .handler = handle_hotplug_event_func,
>>> + .handler = handle_dock_event_func,
>>> };
>>>
>>> /* Check whether the PCI device is managed by native PCIe hotplug driver */
>>>
>>
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