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

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Date:	Fri, 14 Jun 2013 16:12:19 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiang Liu <liuj97@...il.com>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"Alexander E . Patrakov" <patrakov@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Yijing Wang <wangyijing@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	stable@...r.kernel.org
Subject: Re: [BUGFIX 2/9] ACPIPHP: fix device destroying order issue when handling dock notification

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 <jiang.liu@...wei.com>
> >>> Reported-by: Alexander E. Patrakov <patrakov@...il.com>
> >>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> >>> Cc: Yinghai Lu <yinghai@...nel.org>
> >>> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
> >>> Cc: linux-pci@...r.kernel.org
> >>> Cc: linux-kernel@...r.kernel.org
> >>> Cc: stable@...r.kernel.org
> >>> ---
> >>> 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


> > ---
> >  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 */
> > 
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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