Patchwork [Update,3/3] ACPI / dock / PCI: Synchronous handling of dock events for PCI devices

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Submitter Rafael J. Wysocki
Date June 23, 2013, 9:42 p.m.
Message ID <1528326.6SFofebmNT@vostro.rjw.lan>
Download mbox | patch
Permalink /patch/253605/
State Not Applicable
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Rafael J. Wysocki - June 23, 2013, 9:42 p.m.
On Sunday, June 23, 2013 01:29:19 PM Yinghai Lu wrote:
> On Sun, Jun 23, 2013 at 12:57 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> > On Sun, Jun 23, 2013 at 8:54 AM, Jiang Liu <liuj97@gmail.com> wrote:
> >> On 06/23/2013 05:25 AM, Rafael J. Wysocki wrote:
> >>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >>>
> >>> The interactions between the ACPI dock driver and the ACPI-based PCI
> >>> hotplug (acpiphp) are currently problematic because of ordering
> >>> issues during hot-remove operations.
> >>>
> >>> First of all, the current ACPI glue code expects that physical
> >>> devices will always be deleted before deleting the companion ACPI
> >>> device objects.  Otherwise, acpi_unbind_one() will fail with a
> >>> warning message printed to the kernel log, for example:
> >>>
> >>> [  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
> >>>
> >> [...]
> >>> @@ -597,15 +654,11 @@ register_hotplug_dock_device(acpi_handle
> >>>                * ops
> >>>                */
> >>>               dd = find_dock_dependent_device(dock_station, handle);
> >>> -             if (dd) {
> >>> -                     dd->ops = ops;
> >>> -                     dd->context = context;
> >>> -                     dock_add_hotplug_device(dock_station, dd);
> >>> -                     ret = 0;
> >>> -             }
> >>> +             if (dd)
> >>> +                     return dock_init_hotplug(dd, ops, context,
> >>> +                                              init, release);
> >> Hi Rafael,
> >>         Seems not an equivalent change. According to the comment just above the
> >> code, we shouldn't return but continue here.
> >> /*
> >>  * An ATA bay can be in a dock and itself can be ejected
> >>  * separately, so there are two 'dock stations' which need the
> >>  * ops
> >>  */
> >
> > two dock stations:
> > Do you mean two dock station has same handle?
> >
> > dock_add should add correctly flags for IS_DOCK and IS_ATA.
> > if one handle has _DCK and _GTF etc.
> >
> > or do you mean there are two dependent devices with same handle?
> > like one is for acpiphp slot and one is for ATA?
> 
> related commit:
> commit 61b836958371c717d1e6d4fea1d2c512969ad20b
> Author: Shaohua Li <shaohua.li@intel.com>
> Date:   Thu Aug 28 10:07:14 2008 +0800
> 
>     dock: fix for ATA bay in a dock station
> 
>     an ATA bay can be in a dock and itself can be ejected separately.
>     This patch handles such eject bay. Found by Holger.
> 
>     Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>     Signed-off-by: Len Brown <len.brown@intel.com>
> @@ -618,16 +619,21 @@ register_hotplug_dock_device(acpi_handle handle, struct ac
> pi_dock_ops *ops,
>          * this would include the dock station itself
>          */
>         list_for_each_entry(dock_station, &dock_stations, sibiling) {
> +               /*
> +                * An ATA bay can be in a dock and itself can be ejected
> +                * seperately, so there are two 'dock stations' which need the
> +                * ops
> +                */
>                 dd = find_dock_dependent_device(dock_station, handle);
>                 if (dd) {
>                         dd->ops = ops;
>                         dd->context = context;
>                         dock_add_hotplug_device(dock_station, dd);
> -                       return 0;
> +                       ret = 0;
>                 }
>         }
> 
> -       return -EINVAL;
> +       return ret;
>  }
> 
> so two doc station with different handle.
> 
> and dependent devices in both...
> 
> looks like Rafael's change can not handle this case anymore.

Ah, I overlooked the fact that each dock station is on its own dependent_list
and can also be on another dock station's dependent_list.  I'm not sure if that
makes sense, but let's not break the backwards compatibility here.

Updated patch is appended.

Thanks,
Rafael


---
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Subject: ACPI / dock / PCI: Synchronous handling of dock events for PCI devices

The interactions between the ACPI dock driver and the ACPI-based PCI
hotplug (acpiphp) are currently problematic because of ordering
issues during hot-remove operations.

First of all, the current ACPI glue code expects that physical
devices will always be deleted before deleting the companion ACPI
device objects.  Otherwise, acpi_unbind_one() will fail with a
warning message printed to the kernel log, for example:

[  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

This means, in particular, that struct pci_dev objects have to
be deleted before the struct acpi_device objects they are "glued"
with.

Now, the following happens the during the undocking of an ACPI-based
dock station:
 1) hotplug_dock_devices() invokes registered hotplug callbacks to
    destroy physical devices associated with the ACPI device objects
    depending on the dock station.  It calls dd->ops->handler() for
    each of those device objects.
 2) For PCI devices dd->ops->handler() points to
    handle_hotplug_event_func() that queues up a separate work item
    to execute _handle_hotplug_event_func() for the given device and
    returns immediately.  That work item will be executed later.
 3) hotplug_dock_devices() calls dock_remove_acpi_device() for each
    device depending on the dock station.  This runs acpi_bus_trim()
    for each of them, which causes the underlying ACPI device object
    to be destroyed, but the work items queued up by
    handle_hotplug_event_func() haven't been started yet.
 4) _handle_hotplug_event_func() queued up in step 2) are executed
    and cause the above failure to happen, because the PCI devices
    they handle do not have the companion ACPI device objects any
    more (they have been deleted in step 3).

The possible breakage doesn't end here, though, because
hotplug_dock_devices() may return before at least some of the
_handle_hotplug_event_func() work items spawned by it have a
chance to complete and then undock() will cause _DCK to be
evaluated and that will cause the devices handled by the
_handle_hotplug_event_func() to go away possibly while they are
being accessed.

This means that dd->ops->handler() for PCI devices should not point
to handle_hotplug_event_func().  Instead, it should point to a
function that will do the work of _handle_hotplug_event_func()
synchronously.  For this reason, introduce such a function,
hotplug_event_func(), and modity acpiphp_dock_ops to point to
it as the handler.

Unfortunately, however, this is not sufficient, because if the dock
code were not changed further, hotplug_event_func() would now
deadlock with hotplug_dock_devices() that called it, since it would
run unregister_hotplug_dock_device() which in turn would attempt to
acquire the dock station's hp_lock mutex already acquired by
hotplug_dock_devices().

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, during 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.

This change is based on two earlier patches from Jiang Liu.

References: https://bugzilla.kernel.org/show_bug.cgi?id=59501
Reported-and-tested-by: Alexander E. Patrakov <patrakov@gmail.com>
Tracked-down-by: Jiang Liu <jiang.liu@huawei.com>
Tested-by: Illya Klymov <xanf@xanf.me>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: 3.9+ <stable@vger.kernel.org>
---
 drivers/acpi/dock.c                |  141 +++++++++++++++++++++++++------------
 drivers/pci/hotplug/acpiphp_glue.c |   46 ++++++++----
 include/acpi/acpi_drivers.h        |    8 +-
 3 files changed, 135 insertions(+), 60 deletions(-)


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Yinghai Lu - June 23, 2013, 11:04 p.m.
On Sun, Jun 23, 2013 at 2:42 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Sunday, June 23, 2013 01:29:19 PM Yinghai Lu wrote:
>> On Sun, Jun 23, 2013 at 12:57 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> > On Sun, Jun 23, 2013 at 8:54 AM, Jiang Liu <liuj97@gmail.com> wrote:
>> >> On 06/23/2013 05:25 AM, Rafael J. Wysocki wrote:
>> >>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> >>>
>> >>> The interactions between the ACPI dock driver and the ACPI-based PCI
>> >>> hotplug (acpiphp) are currently problematic because of ordering
>> >>> issues during hot-remove operations.
>> >>>
>> >>> First of all, the current ACPI glue code expects that physical
>> >>> devices will always be deleted before deleting the companion ACPI
>> >>> device objects.  Otherwise, acpi_unbind_one() will fail with a
>> >>> warning message printed to the kernel log, for example:
>> >>>
>> >>> [  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
>> >>>
>> >> [...]
>> >>> @@ -597,15 +654,11 @@ register_hotplug_dock_device(acpi_handle
>> >>>                * ops
>> >>>                */
>> >>>               dd = find_dock_dependent_device(dock_station, handle);
>> >>> -             if (dd) {
>> >>> -                     dd->ops = ops;
>> >>> -                     dd->context = context;
>> >>> -                     dock_add_hotplug_device(dock_station, dd);
>> >>> -                     ret = 0;
>> >>> -             }
>> >>> +             if (dd)
>> >>> +                     return dock_init_hotplug(dd, ops, context,
>> >>> +                                              init, release);
>> >> Hi Rafael,
>> >>         Seems not an equivalent change. According to the comment just above the
>> >> code, we shouldn't return but continue here.
>> >> /*
>> >>  * An ATA bay can be in a dock and itself can be ejected
>> >>  * separately, so there are two 'dock stations' which need the
>> >>  * ops
>> >>  */
>> >
>> > two dock stations:
>> > Do you mean two dock station has same handle?
>> >
>> > dock_add should add correctly flags for IS_DOCK and IS_ATA.
>> > if one handle has _DCK and _GTF etc.
>> >
>> > or do you mean there are two dependent devices with same handle?
>> > like one is for acpiphp slot and one is for ATA?
>>
>> related commit:
>> commit 61b836958371c717d1e6d4fea1d2c512969ad20b
>> Author: Shaohua Li <shaohua.li@intel.com>
>> Date:   Thu Aug 28 10:07:14 2008 +0800
>>
>>     dock: fix for ATA bay in a dock station
>>
>>     an ATA bay can be in a dock and itself can be ejected separately.
>>     This patch handles such eject bay. Found by Holger.
>>
>>     Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>>     Signed-off-by: Len Brown <len.brown@intel.com>
>> @@ -618,16 +619,21 @@ register_hotplug_dock_device(acpi_handle handle, struct ac
>> pi_dock_ops *ops,
>>          * this would include the dock station itself
>>          */
>>         list_for_each_entry(dock_station, &dock_stations, sibiling) {
>> +               /*
>> +                * An ATA bay can be in a dock and itself can be ejected
>> +                * seperately, so there are two 'dock stations' which need the
>> +                * ops
>> +                */
>>                 dd = find_dock_dependent_device(dock_station, handle);
>>                 if (dd) {
>>                         dd->ops = ops;
>>                         dd->context = context;
>>                         dock_add_hotplug_device(dock_station, dd);
>> -                       return 0;
>> +                       ret = 0;
>>                 }
>>         }
>>
>> -       return -EINVAL;
>> +       return ret;
>>  }
>>
>> so two doc station with different handle.
>>
>> and dependent devices in both...
>>
>> looks like Rafael's change can not handle this case anymore.
>
> Ah, I overlooked the fact that each dock station is on its own dependent_list
> and can also be on another dock station's dependent_list.  I'm not sure if that
> makes sense, but let's not break the backwards compatibility here.

wonder if dock_release_hotplug with second dock_station and dd will
have problem.

as first one dock_station/dd, could have hp_context release already,
then second one could all release(context) again....

so looks like dock_release_hotplug should go over dock_station/dd list
to clear hp_context in other dock_station/... if they are the same?

Yinghai
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Rafael J. Wysocki - June 24, 2013, 12:40 a.m.
On Sunday, June 23, 2013 04:04:52 PM Yinghai Lu wrote:
> On Sun, Jun 23, 2013 at 2:42 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Sunday, June 23, 2013 01:29:19 PM Yinghai Lu wrote:
> >> On Sun, Jun 23, 2013 at 12:57 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> >> > On Sun, Jun 23, 2013 at 8:54 AM, Jiang Liu <liuj97@gmail.com> wrote:
> >> >> On 06/23/2013 05:25 AM, Rafael J. Wysocki wrote:
> >> >>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> >>>
> >> >>> The interactions between the ACPI dock driver and the ACPI-based PCI
> >> >>> hotplug (acpiphp) are currently problematic because of ordering
> >> >>> issues during hot-remove operations.
> >> >>>
> >> >>> First of all, the current ACPI glue code expects that physical
> >> >>> devices will always be deleted before deleting the companion ACPI
> >> >>> device objects.  Otherwise, acpi_unbind_one() will fail with a
> >> >>> warning message printed to the kernel log, for example:
> >> >>>
> >> >>> [  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
> >> >>>
> >> >> [...]
> >> >>> @@ -597,15 +654,11 @@ register_hotplug_dock_device(acpi_handle
> >> >>>                * ops
> >> >>>                */
> >> >>>               dd = find_dock_dependent_device(dock_station, handle);
> >> >>> -             if (dd) {
> >> >>> -                     dd->ops = ops;
> >> >>> -                     dd->context = context;
> >> >>> -                     dock_add_hotplug_device(dock_station, dd);
> >> >>> -                     ret = 0;
> >> >>> -             }
> >> >>> +             if (dd)
> >> >>> +                     return dock_init_hotplug(dd, ops, context,
> >> >>> +                                              init, release);
> >> >> Hi Rafael,
> >> >>         Seems not an equivalent change. According to the comment just above the
> >> >> code, we shouldn't return but continue here.
> >> >> /*
> >> >>  * An ATA bay can be in a dock and itself can be ejected
> >> >>  * separately, so there are two 'dock stations' which need the
> >> >>  * ops
> >> >>  */
> >> >
> >> > two dock stations:
> >> > Do you mean two dock station has same handle?
> >> >
> >> > dock_add should add correctly flags for IS_DOCK and IS_ATA.
> >> > if one handle has _DCK and _GTF etc.
> >> >
> >> > or do you mean there are two dependent devices with same handle?
> >> > like one is for acpiphp slot and one is for ATA?
> >>
> >> related commit:
> >> commit 61b836958371c717d1e6d4fea1d2c512969ad20b
> >> Author: Shaohua Li <shaohua.li@intel.com>
> >> Date:   Thu Aug 28 10:07:14 2008 +0800
> >>
> >>     dock: fix for ATA bay in a dock station
> >>
> >>     an ATA bay can be in a dock and itself can be ejected separately.
> >>     This patch handles such eject bay. Found by Holger.
> >>
> >>     Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> >>     Signed-off-by: Len Brown <len.brown@intel.com>
> >> @@ -618,16 +619,21 @@ register_hotplug_dock_device(acpi_handle handle, struct ac
> >> pi_dock_ops *ops,
> >>          * this would include the dock station itself
> >>          */
> >>         list_for_each_entry(dock_station, &dock_stations, sibiling) {
> >> +               /*
> >> +                * An ATA bay can be in a dock and itself can be ejected
> >> +                * seperately, so there are two 'dock stations' which need the
> >> +                * ops
> >> +                */
> >>                 dd = find_dock_dependent_device(dock_station, handle);
> >>                 if (dd) {
> >>                         dd->ops = ops;
> >>                         dd->context = context;
> >>                         dock_add_hotplug_device(dock_station, dd);
> >> -                       return 0;
> >> +                       ret = 0;
> >>                 }
> >>         }
> >>
> >> -       return -EINVAL;
> >> +       return ret;
> >>  }
> >>
> >> so two doc station with different handle.
> >>
> >> and dependent devices in both...
> >>
> >> looks like Rafael's change can not handle this case anymore.
> >
> > Ah, I overlooked the fact that each dock station is on its own dependent_list
> > and can also be on another dock station's dependent_list.  I'm not sure if that
> > makes sense, but let's not break the backwards compatibility here.
> 
> wonder if dock_release_hotplug with second dock_station and dd will
> have problem.
> 
> as first one dock_station/dd, could have hp_context release already,
> then second one could all release(context) again....
> 
> so looks like dock_release_hotplug should go over dock_station/dd list
> to clear hp_context in other dock_station/... if they are the same?

I'm not sure what you mean.  They are different dependent_device objects
and each of them has its own context pointer, although they both will point to
the same thing.

Both "init" and "release" will be called for each of them individually which
for for acpiphp (which is the only user of that ATM) actually means "get" and
"put", so it should be OK.

Thanks,
Rafael
Yinghai Lu - June 24, 2013, 4:34 a.m.
On Sun, Jun 23, 2013 at 5:40 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Sunday, June 23, 2013 04:04:52 PM Yinghai Lu wrote:
>> On Sun, Jun 23, 2013 at 2:42 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
...
>> > Ah, I overlooked the fact that each dock station is on its own dependent_list
>> > and can also be on another dock station's dependent_list.  I'm not sure if that
>> > makes sense, but let's not break the backwards compatibility here.
>>
>> wonder if dock_release_hotplug with second dock_station and dd will
>> have problem.
>>
>> as first one dock_station/dd, could have hp_context release already,
>> then second one could all release(context) again....
>>
>> so looks like dock_release_hotplug should go over dock_station/dd list
>> to clear hp_context in other dock_station/... if they are the same?
>
> I'm not sure what you mean.  They are different dependent_device objects
> and each of them has its own context pointer, although they both will point to
> the same thing.
>
> Both "init" and "release" will be called for each of them individually which
> for for acpiphp (which is the only user of that ATM) actually means "get" and
> "put", so it should be OK.

yes, then hp_context can never be  the same, just the acpi handle is the same.

Acked-by: Yinghai Lu <yinghai@kernel.org>

BTW, thank you very much for the whole acpi scan rework.

Yinghai
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Rafael J. Wysocki - June 24, 2013, 9:55 a.m.
On Sunday, June 23, 2013 09:34:09 PM Yinghai Lu wrote:
> On Sun, Jun 23, 2013 at 5:40 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Sunday, June 23, 2013 04:04:52 PM Yinghai Lu wrote:
> >> On Sun, Jun 23, 2013 at 2:42 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> ...
> >> > Ah, I overlooked the fact that each dock station is on its own dependent_list
> >> > and can also be on another dock station's dependent_list.  I'm not sure if that
> >> > makes sense, but let's not break the backwards compatibility here.
> >>
> >> wonder if dock_release_hotplug with second dock_station and dd will
> >> have problem.
> >>
> >> as first one dock_station/dd, could have hp_context release already,
> >> then second one could all release(context) again....
> >>
> >> so looks like dock_release_hotplug should go over dock_station/dd list
> >> to clear hp_context in other dock_station/... if they are the same?
> >
> > I'm not sure what you mean.  They are different dependent_device objects
> > and each of them has its own context pointer, although they both will point to
> > the same thing.
> >
> > Both "init" and "release" will be called for each of them individually which
> > for for acpiphp (which is the only user of that ATM) actually means "get" and
> > "put", so it should be OK.
> 
> yes, then hp_context can never be  the same, just the acpi handle is the same.
> 
> Acked-by: Yinghai Lu <yinghai@kernel.org>

Thanks!

> BTW, thank you very much for the whole acpi scan rework.

Well, no problem, it was necessary for a number of reasons.

And honestly I think more along those lines is still needed. :-)

For example, the discussion here shows how fragile the design of acpiphp is.
Take hotplug_dock_devices() for instance.  It shouldn't even need to use those
"handlers", because ideally acpi_bus_trim() should automatically trigger the
removal of "physical" device objects depending on the stuff being trimmed.
And analogously for acpi_bus_scan().

The "trim" part should be possible to implement even now, because
struct acpi_device contains a "remove" callback pointer (that was added for
power resources IIRC), although perhaps it'll need to be called from
acpi_bus_device_detach().  The "scan" part should be doable too if we add
an "add child" callback to struct acpi_device, so that acpi_bus_device_attach()
can use it to handle devices that don't have scan handlers or ACPI drivers
(like PCI devices).

Thanks,
Rafael

Patch

Index: linux-pm/drivers/acpi/dock.c
===================================================================
--- linux-pm.orig/drivers/acpi/dock.c
+++ linux-pm/drivers/acpi/dock.c
@@ -66,20 +66,21 @@  struct dock_station {
 	spinlock_t dd_lock;
 	struct mutex hp_lock;
 	struct list_head dependent_devices;
-	struct list_head hotplug_devices;
 
 	struct list_head sibling;
 	struct platform_device *dock_device;
 };
 static LIST_HEAD(dock_stations);
 static int dock_station_count;
+static DEFINE_MUTEX(hotplug_lock);
 
 struct dock_dependent_device {
 	struct list_head list;
-	struct list_head hotplug_list;
 	acpi_handle handle;
-	const struct acpi_dock_ops *ops;
-	void *context;
+	const struct acpi_dock_ops *hp_ops;
+	void *hp_context;
+	unsigned int hp_refcount;
+	void (*hp_release)(void *);
 };
 
 #define DOCK_DOCKING	0x00000001
@@ -111,7 +112,6 @@  add_dock_dependent_device(struct dock_st
 
 	dd->handle = handle;
 	INIT_LIST_HEAD(&dd->list);
-	INIT_LIST_HEAD(&dd->hotplug_list);
 
 	spin_lock(&ds->dd_lock);
 	list_add_tail(&dd->list, &ds->dependent_devices);
@@ -121,35 +121,90 @@  add_dock_dependent_device(struct dock_st
 }
 
 /**
- * dock_add_hotplug_device - associate a hotplug handler with the dock station
- * @ds: The dock station
- * @dd: The dependent device struct
- *
- * Add the dependent device to the dock's hotplug device list
- */
-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);
+ * dock_init_hotplug - Initialize a hotplug device on a docking station.
+ * @dd: Dock-dependent device.
+ * @ops: Dock operations to attach to the dependent device.
+ * @context: Data to pass to the @ops callbacks and @release.
+ * @init: Optional initialization routine to run after setting up context.
+ * @release: Optional release routine to run on removal.
+ */
+static int dock_init_hotplug(struct dock_dependent_device *dd,
+			     const struct acpi_dock_ops *ops, void *context,
+			     void (*init)(void *), void (*release)(void *))
+{
+	int ret = 0;
+
+	mutex_lock(&hotplug_lock);
+
+	if (dd->hp_context) {
+		ret = -EEXIST;
+	} else {
+		dd->hp_refcount = 1;
+		dd->hp_ops = ops;
+		dd->hp_context = context;
+		dd->hp_release = release;
+	}
+
+	if (!WARN_ON(ret) && init)
+		init(context);
+
+	mutex_unlock(&hotplug_lock);
+	return ret;
 }
 
 /**
- * dock_del_hotplug_device - remove a hotplug handler from the dock station
- * @ds: The dock station
- * @dd: the dependent device struct
+ * dock_release_hotplug - Decrement hotplug reference counter of dock device.
+ * @dd: Dock-dependent device.
  *
- * Delete the dependent device from the dock's hotplug device list
+ * Decrement the reference counter of @dd and if 0, detach its hotplug
+ * operations from it, reset its context pointer and run the optional release
+ * routine if present.
  */
-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);
 }
 
 /**
@@ -360,9 +415,8 @@  static void hotplug_dock_devices(struct
 	/*
 	 * First call driver specific hotplug functions
 	 */
-	list_for_each_entry(dd, &ds->hotplug_devices, hotplug_list)
-		if (dd->ops && dd->ops->handler)
-			dd->ops->handler(dd->handle, event, dd->context);
+	list_for_each_entry(dd, &ds->dependent_devices, list)
+		dock_hotplug_event(dd, event, false);
 
 	/*
 	 * Now make sure that an acpi_device is created for each
@@ -398,9 +452,8 @@  static void dock_event(struct dock_stati
 	if (num == DOCK_EVENT)
 		kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
 
-	list_for_each_entry(dd, &ds->hotplug_devices, hotplug_list)
-		if (dd->ops && dd->ops->uevent)
-			dd->ops->uevent(dd->handle, event, dd->context);
+	list_for_each_entry(dd, &ds->dependent_devices, list)
+		dock_hotplug_event(dd, event, true);
 
 	if (num != DOCK_EVENT)
 		kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
@@ -570,19 +623,24 @@  EXPORT_SYMBOL_GPL(unregister_dock_notifi
  * @handle: the handle of the device
  * @ops: handlers to call after docking
  * @context: device specific data
+ * @init: Optional initialization routine to run after registration
+ * @release: Optional release routine to run on unregistration
  *
  * If a driver would like to perform a hotplug operation after a dock
  * event, they can register an acpi_notifiy_handler to be called by
  * the dock driver after _DCK is executed.
  */
-int
-register_hotplug_dock_device(acpi_handle handle, const struct acpi_dock_ops *ops,
-			     void *context)
+int register_hotplug_dock_device(acpi_handle handle,
+				 const struct acpi_dock_ops *ops, void *context,
+				 void (*init)(void *), void (*release)(void *))
 {
 	struct dock_dependent_device *dd;
 	struct dock_station *dock_station;
 	int ret = -EINVAL;
 
+	if (WARN_ON(!context))
+		return -EINVAL;
+
 	if (!dock_station_count)
 		return -ENODEV;
 
@@ -597,12 +655,8 @@  register_hotplug_dock_device(acpi_handle
 		 * ops
 		 */
 		dd = find_dock_dependent_device(dock_station, handle);
-		if (dd) {
-			dd->ops = ops;
-			dd->context = context;
-			dock_add_hotplug_device(dock_station, dd);
+		if (dd && !dock_init_hotplug(dd, ops, context, init, release))
 			ret = 0;
-		}
 	}
 
 	return ret;
@@ -624,7 +678,7 @@  void unregister_hotplug_dock_device(acpi
 	list_for_each_entry(dock_station, &dock_stations, sibling) {
 		dd = find_dock_dependent_device(dock_station, handle);
 		if (dd)
-			dock_del_hotplug_device(dock_station, dd);
+			dock_release_hotplug(dd);
 	}
 }
 EXPORT_SYMBOL_GPL(unregister_hotplug_dock_device);
@@ -953,7 +1007,6 @@  static int __init dock_add(acpi_handle h
 	mutex_init(&dock_station->hp_lock);
 	spin_lock_init(&dock_station->dd_lock);
 	INIT_LIST_HEAD(&dock_station->sibling);
-	INIT_LIST_HEAD(&dock_station->hotplug_devices);
 	ATOMIC_INIT_NOTIFIER_HEAD(&dock_notifier_list);
 	INIT_LIST_HEAD(&dock_station->dependent_devices);
 
Index: linux-pm/include/acpi/acpi_drivers.h
===================================================================
--- linux-pm.orig/include/acpi/acpi_drivers.h
+++ linux-pm/include/acpi/acpi_drivers.h
@@ -123,7 +123,9 @@  extern int register_dock_notifier(struct
 extern void unregister_dock_notifier(struct notifier_block *nb);
 extern int register_hotplug_dock_device(acpi_handle handle,
 					const struct acpi_dock_ops *ops,
-					void *context);
+					void *context,
+					void (*init)(void *),
+					void (*release)(void *));
 extern void unregister_hotplug_dock_device(acpi_handle handle);
 #else
 static inline int is_dock_device(acpi_handle handle)
@@ -139,7 +141,9 @@  static inline void unregister_dock_notif
 }
 static inline int register_hotplug_dock_device(acpi_handle handle,
 					       const struct acpi_dock_ops *ops,
-					       void *context)
+					       void *context,
+					       void (*init)(void *),
+					       void (*release)(void *))
 {
 	return -ENODEV;
 }
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
@@ -61,6 +61,7 @@  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 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 +148,7 @@  static int post_dock_fixups(struct notif
 
 
 static const struct acpi_dock_ops acpiphp_dock_ops = {
-	.handler = handle_hotplug_event_func,
+	.handler = hotplug_event_func,
 };
 
 /* Check whether the PCI device is managed by native PCIe hotplug driver */
@@ -179,6 +180,20 @@  static bool device_is_managed_by_native_
 	return true;
 }
 
+static void acpiphp_dock_init(void *data)
+{
+	struct acpiphp_func *func = data;
+
+	get_bridge(func->slot->bridge);
+}
+
+static void acpiphp_dock_release(void *data)
+{
+	struct acpiphp_func *func = data;
+
+	put_bridge(func->slot->bridge);
+}
+
 /* callback routine to register each ACPI PCI slot object */
 static acpi_status
 register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
@@ -298,7 +313,8 @@  register_slot(acpi_handle handle, u32 lv
 		 */
 		newfunc->flags &= ~FUNC_HAS_EJ0;
 		if (register_hotplug_dock_device(handle,
-			&acpiphp_dock_ops, newfunc))
+			&acpiphp_dock_ops, newfunc,
+			acpiphp_dock_init, acpiphp_dock_release))
 			dbg("failed to register dock device\n");
 
 		/* we need to be notified when dock events happen
@@ -1068,22 +1084,12 @@  static void handle_hotplug_event_bridge(
 	alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_bridge);
 }
 
-static void _handle_hotplug_event_func(struct work_struct *work)
+static void 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);
 
@@ -1116,6 +1122,18 @@  static void _handle_hotplug_event_func(s
 		warn("notify_handler: unknown event type 0x%x for %s\n", type, objname);
 		break;
 	}
+}
+
+static void _handle_hotplug_event_func(struct work_struct *work)
+{
+	struct acpi_hp_work *hp_work;
+	struct acpiphp_func *func;
+
+	hp_work = container_of(work, struct acpi_hp_work, work);
+	func = hp_work->context;
+	acpi_scan_lock_acquire();
+
+	hotplug_event_func(hp_work->handle, hp_work->type, func);
 
 	acpi_scan_lock_release();
 	kfree(hp_work); /* allocated in handle_hotplug_event_func */