* [PATCH] cpuidle: Check for dev before deregistering it.
@ 2013-12-03 15:59 Konrad Rzeszutek Wilk
2013-12-03 21:33 ` Rafael J. Wysocki
0 siblings, 1 reply; 6+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-12-03 15:59 UTC (permalink / raw)
To: rjw, linux-pm, linux-kernel
Cc: xen-devel, Konrad Rzeszutek Wilk, Daniel Lezcano
If not, we could end up in the unfortunate situation where
we dereference a NULL pointer b/c we have cpuidle disabled.
This is the case when booting under Xen (which uses the
ACPI P/C states but disables the CPU idle driver) - and can
be easily reproduced when booting with cpuidle.off=1.
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
.. snip..
Call Trace:
[<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
[<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
[<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
[<ffffffff81420ed8>] bus_remove_device+0x108/0x180
[<ffffffff8141d9d9>] device_del+0x129/0x1c0
[<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
[<ffffffff8141da8e>] device_unregister+0x1e/0x60
[<ffffffff814243e9>] unregister_cpu+0x39/0x60
[<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
[<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
[<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
[<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
[<ffffffff8108ec42>] kthread+0xd2/0xf0
[<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
[<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
[<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
This problem also appears in 3.12 and could be a candidate for backport.
CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
CC: Daniel Lezcano <daniel.lezcano@linaro.org>
CC: linux-pm@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/cpuidle/cpuidle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 2a991e4..a55e68f 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
*/
void cpuidle_unregister_device(struct cpuidle_device *dev)
{
- if (dev->registered == 0)
+ if (!dev || dev->registered == 0)
return;
cpuidle_pause_and_lock();
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] cpuidle: Check for dev before deregistering it.
2013-12-03 15:59 [PATCH] cpuidle: Check for dev before deregistering it Konrad Rzeszutek Wilk
@ 2013-12-03 21:33 ` Rafael J. Wysocki
2013-12-04 9:10 ` Daniel Lezcano
0 siblings, 1 reply; 6+ messages in thread
From: Rafael J. Wysocki @ 2013-12-03 21:33 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk; +Cc: linux-pm, linux-kernel, xen-devel, Daniel Lezcano
On Tuesday, December 03, 2013 10:59:58 AM Konrad Rzeszutek Wilk wrote:
> If not, we could end up in the unfortunate situation where
> we dereference a NULL pointer b/c we have cpuidle disabled.
>
> This is the case when booting under Xen (which uses the
> ACPI P/C states but disables the CPU idle driver) - and can
> be easily reproduced when booting with cpuidle.off=1.
>
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
> .. snip..
> Call Trace:
> [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
> [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
> [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
> [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
> [<ffffffff8141d9d9>] device_del+0x129/0x1c0
> [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
> [<ffffffff8141da8e>] device_unregister+0x1e/0x60
> [<ffffffff814243e9>] unregister_cpu+0x39/0x60
> [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
> [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
> [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
> [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
> [<ffffffff8108ec42>] kthread+0xd2/0xf0
> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
> [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
>
> This problem also appears in 3.12 and could be a candidate for backport.
>
> CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> CC: Daniel Lezcano <daniel.lezcano@linaro.org>
> CC: linux-pm@vger.kernel.org
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Applied, thanks!
> ---
> drivers/cpuidle/cpuidle.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 2a991e4..a55e68f 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
> */
> void cpuidle_unregister_device(struct cpuidle_device *dev)
> {
> - if (dev->registered == 0)
> + if (!dev || dev->registered == 0)
> return;
>
> cpuidle_pause_and_lock();
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpuidle: Check for dev before deregistering it.
2013-12-03 21:33 ` Rafael J. Wysocki
@ 2013-12-04 9:10 ` Daniel Lezcano
2013-12-04 16:09 ` Konrad Rzeszutek Wilk
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Lezcano @ 2013-12-04 9:10 UTC (permalink / raw)
To: Rafael J. Wysocki, Konrad Rzeszutek Wilk
Cc: linux-pm, linux-kernel, xen-devel
On 12/03/2013 10:33 PM, Rafael J. Wysocki wrote:
> On Tuesday, December 03, 2013 10:59:58 AM Konrad Rzeszutek Wilk wrote:
>> If not, we could end up in the unfortunate situation where
>> we dereference a NULL pointer b/c we have cpuidle disabled.
>>
>> This is the case when booting under Xen (which uses the
>> ACPI P/C states but disables the CPU idle driver) - and can
>> be easily reproduced when booting with cpuidle.off=1.
>>
>> BUG: unable to handle kernel NULL pointer dereference at (null)
>> IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
>> .. snip..
>> Call Trace:
>> [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
>> [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
>> [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
>> [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
>> [<ffffffff8141d9d9>] device_del+0x129/0x1c0
>> [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
>> [<ffffffff8141da8e>] device_unregister+0x1e/0x60
>> [<ffffffff814243e9>] unregister_cpu+0x39/0x60
>> [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
>> [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
>> [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
>> [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
>> [<ffffffff8108ec42>] kthread+0xd2/0xf0
>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
>> [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
>>
>> This problem also appears in 3.12 and could be a candidate for backport.
>>
>> CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>> CC: Daniel Lezcano <daniel.lezcano@linaro.org>
>> CC: linux-pm@vger.kernel.org
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
> Applied, thanks!
>
>> ---
>> drivers/cpuidle/cpuidle.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
>> index 2a991e4..a55e68f 100644
>> --- a/drivers/cpuidle/cpuidle.c
>> +++ b/drivers/cpuidle/cpuidle.c
>> @@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
>> */
>> void cpuidle_unregister_device(struct cpuidle_device *dev)
>> {
>> - if (dev->registered == 0)
>> + if (!dev || dev->registered == 0)
>> return;
>>
>> cpuidle_pause_and_lock();
Oops, wait. Are we sure the problem is coming from cpuidle ?
The cpuidle_unregister_device is called with a NULL pointer, that
shouldn't happen.
Konrad, you say that could be easily reproduced. How do you produce it ?
Unplugging a cpu ?
--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpuidle: Check for dev before deregistering it.
2013-12-04 9:10 ` Daniel Lezcano
@ 2013-12-04 16:09 ` Konrad Rzeszutek Wilk
2013-12-04 21:24 ` Daniel Lezcano
0 siblings, 1 reply; 6+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-12-04 16:09 UTC (permalink / raw)
To: Daniel Lezcano; +Cc: Rafael J. Wysocki, linux-pm, linux-kernel, xen-devel
On Wed, Dec 04, 2013 at 10:10:28AM +0100, Daniel Lezcano wrote:
> On 12/03/2013 10:33 PM, Rafael J. Wysocki wrote:
> >On Tuesday, December 03, 2013 10:59:58 AM Konrad Rzeszutek Wilk wrote:
> >>If not, we could end up in the unfortunate situation where
> >>we dereference a NULL pointer b/c we have cpuidle disabled.
> >>
> >>This is the case when booting under Xen (which uses the
> >>ACPI P/C states but disables the CPU idle driver) - and can
> >>be easily reproduced when booting with cpuidle.off=1.
> >>
> >>BUG: unable to handle kernel NULL pointer dereference at (null)
> >>IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
> >>.. snip..
> >>Call Trace:
> >> [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
> >> [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
> >> [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
> >> [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
> >> [<ffffffff8141d9d9>] device_del+0x129/0x1c0
> >> [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
> >> [<ffffffff8141da8e>] device_unregister+0x1e/0x60
> >> [<ffffffff814243e9>] unregister_cpu+0x39/0x60
> >> [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
> >> [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
> >> [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
> >> [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
> >> [<ffffffff8108ec42>] kthread+0xd2/0xf0
> >> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
> >> [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
> >> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
> >>
> >>This problem also appears in 3.12 and could be a candidate for backport.
> >>
> >>CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> >>CC: Daniel Lezcano <daniel.lezcano@linaro.org>
> >>CC: linux-pm@vger.kernel.org
> >>Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >
> >Applied, thanks!
> >
> >>---
> >> drivers/cpuidle/cpuidle.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> >>index 2a991e4..a55e68f 100644
> >>--- a/drivers/cpuidle/cpuidle.c
> >>+++ b/drivers/cpuidle/cpuidle.c
> >>@@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
> >> */
> >> void cpuidle_unregister_device(struct cpuidle_device *dev)
> >> {
> >>- if (dev->registered == 0)
> >>+ if (!dev || dev->registered == 0)
> >> return;
> >>
> >> cpuidle_pause_and_lock();
>
> Oops, wait. Are we sure the problem is coming from cpuidle ?
It is acpi_processor_power_exit assuming that the cpuidle is
initialized. It could be fixed there too, but there are multiple
entries in cpuidle where it does the : "if (!dev) return .."
so I figured this should be done as well here.
>
> The cpuidle_unregister_device is called with a NULL pointer, that
> shouldn't happen.
It does :-)
>
> Konrad, you say that could be easily reproduced. How do you produce
> it ? Unplugging a cpu ?
Yes.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpuidle: Check for dev before deregistering it.
2013-12-04 16:09 ` Konrad Rzeszutek Wilk
@ 2013-12-04 21:24 ` Daniel Lezcano
2013-12-04 22:46 ` Rafael J. Wysocki
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Lezcano @ 2013-12-04 21:24 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk
Cc: Rafael J. Wysocki, linux-pm, linux-kernel, xen-devel
On 12/04/2013 05:09 PM, Konrad Rzeszutek Wilk wrote:
> On Wed, Dec 04, 2013 at 10:10:28AM +0100, Daniel Lezcano wrote:
>> On 12/03/2013 10:33 PM, Rafael J. Wysocki wrote:
>>> On Tuesday, December 03, 2013 10:59:58 AM Konrad Rzeszutek Wilk wrote:
>>>> If not, we could end up in the unfortunate situation where
>>>> we dereference a NULL pointer b/c we have cpuidle disabled.
>>>>
>>>> This is the case when booting under Xen (which uses the
>>>> ACPI P/C states but disables the CPU idle driver) - and can
>>>> be easily reproduced when booting with cpuidle.off=1.
>>>>
>>>> BUG: unable to handle kernel NULL pointer dereference at (null)
>>>> IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
>>>> .. snip..
>>>> Call Trace:
>>>> [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
>>>> [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
>>>> [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
>>>> [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
>>>> [<ffffffff8141d9d9>] device_del+0x129/0x1c0
>>>> [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
>>>> [<ffffffff8141da8e>] device_unregister+0x1e/0x60
>>>> [<ffffffff814243e9>] unregister_cpu+0x39/0x60
>>>> [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
>>>> [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
>>>> [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
>>>> [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
>>>> [<ffffffff8108ec42>] kthread+0xd2/0xf0
>>>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
>>>> [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
>>>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
>>>>
>>>> This problem also appears in 3.12 and could be a candidate for backport.
>>>>
>>>> CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
>>>> CC: Daniel Lezcano <daniel.lezcano@linaro.org>
>>>> CC: linux-pm@vger.kernel.org
>>>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>>
>>> Applied, thanks!
>>>
>>>> ---
>>>> drivers/cpuidle/cpuidle.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
>>>> index 2a991e4..a55e68f 100644
>>>> --- a/drivers/cpuidle/cpuidle.c
>>>> +++ b/drivers/cpuidle/cpuidle.c
>>>> @@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
>>>> */
>>>> void cpuidle_unregister_device(struct cpuidle_device *dev)
>>>> {
>>>> - if (dev->registered == 0)
>>>> + if (!dev || dev->registered == 0)
>>>> return;
>>>>
>>>> cpuidle_pause_and_lock();
>>
>> Oops, wait. Are we sure the problem is coming from cpuidle ?
>
> It is acpi_processor_power_exit assuming that the cpuidle is
> initialized. It could be fixed there too, but there are multiple
> entries in cpuidle where it does the : "if (!dev) return .."
> so I figured this should be done as well here.
I understand.
From my POV the bug is coming from the acpi processor idle driver.
The function acpi_processor_power_init registers the cpuidle driver and
the cpuidle device when acpi_processor_registered is zero. Then it
increments acpi_processor_registered preventing the next call to this
function to register the driver but it will register the device.
As cpuidle is disabled, the cpuidle_register_driver fails, thus the
device is not registered and acpi_processor_registered is not
incremented. So all calls to acpi_processor_power_init prevents the
driver and the device to be registered. No problem with that.
But the function acpi_processor_power_exit does not take care of the
value of acpi_processor_registered and just unregister the device. Then
it decrements acpi_processor_registered which is zero to -1.
Trying to be immune from a NULL pointer in cpuidle_unregister_device
hides bogus code from the caller. So IMO, this check shouldn't be there
and the acpi_processor_power_exit function should be fixed instead.
>> The cpuidle_unregister_device is called with a NULL pointer, that
>> shouldn't happen.
>
> It does :-)
>>
>> Konrad, you say that could be easily reproduced. How do you produce
>> it ? Unplugging a cpu ?
>
> Yes.
>
--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpuidle: Check for dev before deregistering it.
2013-12-04 21:24 ` Daniel Lezcano
@ 2013-12-04 22:46 ` Rafael J. Wysocki
0 siblings, 0 replies; 6+ messages in thread
From: Rafael J. Wysocki @ 2013-12-04 22:46 UTC (permalink / raw)
To: Daniel Lezcano; +Cc: Konrad Rzeszutek Wilk, linux-pm, linux-kernel, xen-devel
On Wednesday, December 04, 2013 10:24:25 PM Daniel Lezcano wrote:
> On 12/04/2013 05:09 PM, Konrad Rzeszutek Wilk wrote:
> > On Wed, Dec 04, 2013 at 10:10:28AM +0100, Daniel Lezcano wrote:
> >> On 12/03/2013 10:33 PM, Rafael J. Wysocki wrote:
> >>> On Tuesday, December 03, 2013 10:59:58 AM Konrad Rzeszutek Wilk wrote:
> >>>> If not, we could end up in the unfortunate situation where
> >>>> we dereference a NULL pointer b/c we have cpuidle disabled.
> >>>>
> >>>> This is the case when booting under Xen (which uses the
> >>>> ACPI P/C states but disables the CPU idle driver) - and can
> >>>> be easily reproduced when booting with cpuidle.off=1.
> >>>>
> >>>> BUG: unable to handle kernel NULL pointer dereference at (null)
> >>>> IP: [<ffffffff8156db4a>] cpuidle_unregister_device+0x2a/0x90
> >>>> .. snip..
> >>>> Call Trace:
> >>>> [<ffffffff813b15b4>] acpi_processor_power_exit+0x3c/0x5c
> >>>> [<ffffffff813af0a9>] acpi_processor_stop+0x61/0xb6
> >>>> [<ffffffff814215bf>] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30
> >>>> [<ffffffff81420ed8>] bus_remove_device+0x108/0x180
> >>>> [<ffffffff8141d9d9>] device_del+0x129/0x1c0
> >>>> [<ffffffff813cb4b0>] ? unregister_xenbus_watch+0x1f0/0x1f0
> >>>> [<ffffffff8141da8e>] device_unregister+0x1e/0x60
> >>>> [<ffffffff814243e9>] unregister_cpu+0x39/0x60
> >>>> [<ffffffff81019e03>] arch_unregister_cpu+0x23/0x30
> >>>> [<ffffffff813c3c51>] handle_vcpu_hotplug_event+0xc1/0xe0
> >>>> [<ffffffff813cb4f5>] xenwatch_thread+0x45/0x120
> >>>> [<ffffffff810af010>] ? abort_exclusive_wait+0xb0/0xb0
> >>>> [<ffffffff8108ec42>] kthread+0xd2/0xf0
> >>>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
> >>>> [<ffffffff816ce17c>] ret_from_fork+0x7c/0xb0
> >>>> [<ffffffff8108eb70>] ? kthread_create_on_node+0x180/0x180
> >>>>
> >>>> This problem also appears in 3.12 and could be a candidate for backport.
> >>>>
> >>>> CC: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> >>>> CC: Daniel Lezcano <daniel.lezcano@linaro.org>
> >>>> CC: linux-pm@vger.kernel.org
> >>>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >>>
> >>> Applied, thanks!
> >>>
> >>>> ---
> >>>> drivers/cpuidle/cpuidle.c | 2 +-
> >>>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> >>>> index 2a991e4..a55e68f 100644
> >>>> --- a/drivers/cpuidle/cpuidle.c
> >>>> +++ b/drivers/cpuidle/cpuidle.c
> >>>> @@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device);
> >>>> */
> >>>> void cpuidle_unregister_device(struct cpuidle_device *dev)
> >>>> {
> >>>> - if (dev->registered == 0)
> >>>> + if (!dev || dev->registered == 0)
> >>>> return;
> >>>>
> >>>> cpuidle_pause_and_lock();
> >>
> >> Oops, wait. Are we sure the problem is coming from cpuidle ?
> >
> > It is acpi_processor_power_exit assuming that the cpuidle is
> > initialized. It could be fixed there too, but there are multiple
> > entries in cpuidle where it does the : "if (!dev) return .."
> > so I figured this should be done as well here.
>
> I understand.
>
> From my POV the bug is coming from the acpi processor idle driver.
>
> The function acpi_processor_power_init registers the cpuidle driver and
> the cpuidle device when acpi_processor_registered is zero. Then it
> increments acpi_processor_registered preventing the next call to this
> function to register the driver but it will register the device.
>
> As cpuidle is disabled, the cpuidle_register_driver fails, thus the
> device is not registered and acpi_processor_registered is not
> incremented. So all calls to acpi_processor_power_init prevents the
> driver and the device to be registered. No problem with that.
>
> But the function acpi_processor_power_exit does not take care of the
> value of acpi_processor_registered and just unregister the device. Then
> it decrements acpi_processor_registered which is zero to -1.
>
> Trying to be immune from a NULL pointer in cpuidle_unregister_device
> hides bogus code from the caller. So IMO, this check shouldn't be there
> and the acpi_processor_power_exit function should be fixed instead.
I'm not sure I understand the "hides bogus code from the caller" phrase.
It prevents the kernel from crashing, which may be due to a driver bug, but
still.
We can add a WARN_ON() around the check to indicate suspiciousness, but
otherwise I don't have problems with preventing kernel crashes from
happening.
Thanks,
Rafael
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-12-04 22:33 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-12-03 15:59 [PATCH] cpuidle: Check for dev before deregistering it Konrad Rzeszutek Wilk
2013-12-03 21:33 ` Rafael J. Wysocki
2013-12-04 9:10 ` Daniel Lezcano
2013-12-04 16:09 ` Konrad Rzeszutek Wilk
2013-12-04 21:24 ` Daniel Lezcano
2013-12-04 22:46 ` Rafael J. Wysocki
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