Re: [Intel-gfx] WQ_UNBOUND warning since recent workqueue refactoring
On 30.08.2023 20:56, Imre Deak wrote:
> On Wed, Aug 30, 2023 at 07:51:13AM -1000, Tejun Heo wrote:
> Hi,
>
>> Hello,
>>
>> (cc'ing i915 folks)
>>
>> On Wed, Aug 30, 2023 at 04:57:42PM +0200, Heiner Kallweit wrote:
>>> Recently I started to see the following warning on linux-next and presumably
>>> this may be related to the refactoring of the workqueue core code.
>>>
>>> [ 56.900223] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
>>> for >1us 4 times, consider switching to WQ_UNBOUND
>>> [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
>>> >1us 4 times, consider switching to WQ_UNBOUND
>>> [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
>>> for >1us 8 times, consider switching to WQ_UNBOUND
>>> [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
>>> >1us 8 times, consider switching to WQ_UNBOUND
>>>
>>> Adding WQ_UNBOUND to these queues didn't change the behavior.
>>
>> That should have made them go away as the code path isn't active at all for
>> WQ_UNBOUND workqueues. Can you please double check?
>>
I tried the patch given below and double-checked. No change in behavior.
>>> Maybe relevant: I run the affected system headless.
>>
>> i915 folks, workqueue recently added debug warnings which trigger when a
>> per-cpu work item hogs the CPU for too long - 10ms in this case. This is
>> problematic because such work item can stall other per-cpu work items.
>>
>> * Is it expected for the above two work functions to occupy the CPU for over
>> 10ms repeatedly?
>
> No, this shouldn't happen.
>
> I assume it happens in
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>
> after cfd48ad8c4a9 ("drm/i915: Fix HPD polling, reenabling the output poll
> work as needed")
>
> which could result in the above problem.
>
> Could you give a try to
> https://lore.kernel.org/all/20230809104307.1218058-1-imre.d...@intel.com/
>
Didn't help
> and if that doesn't help provide more information/logs, by opening a
> ticket at:
> https://gitlab.freedesktop.org/drm/intel/-/issues/new
>
> Thanks,
> Imre
>
>> * If so, can we make them use an unbound workqueue instead?
>>
>> Thanks.
>>
>> --
>> tejun
diff --git a/drivers/gpu/drm/drm_probe_helper.c
b/drivers/gpu/drm/drm_probe_helper.c
index 3f479483d..ac28b8d0f 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -279,7 +279,7 @@ static void reschedule_output_poll_work(struct drm_device
*dev)
*/
delay = HZ;
- schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
+ queue_delayed_work(system_unbound_wq,
&dev->mode_config.output_poll_work, delay);
}
/**
@@ -614,7 +614,7 @@ int drm_helper_probe_single_connector_modes(struct
drm_connector *connector,
*/
dev->mode_config.delayed_event = true;
if (dev->mode_config.poll_enabled)
- mod_delayed_work(system_wq,
+ mod_delayed_work(system_unbound_wq,
&dev->mode_config.output_poll_work,
0);
}
diff --git a/drivers/gpu/drm/i915/i915_driver.c
b/drivers/gpu/drm/i915/i915_driver.c
index ec4d26b3c..c0592b77b 100644
--- a/drivers/gpu/drm/i915/i915_driver.c
+++ b/drivers/gpu/drm/i915/i915_driver.c
@@ -138,7 +138,7 @@ static int i915_workqueues_init(struct drm_i915_private
*dev_priv)
* to be scheduled on the system_wq before moving to a driver
* instance due deprecation of flush_scheduled_work().
*/
- dev_priv->unordered_wq = alloc_workqueue("i915-unordered", 0, 0);
+ dev_priv->unordered_wq = alloc_workqueue("i915-unordered", WQ_UNBOUND,
0);
if (dev_priv->unordered_wq == NULL)
goto out_free_dp_wq;
--
2.42.0
Re: [Intel-gfx] WQ_UNBOUND warning since recent workqueue refactoring
On 30.08.2023 20:56, Imre Deak wrote:
> On Wed, Aug 30, 2023 at 07:51:13AM -1000, Tejun Heo wrote:
> Hi,
>
>> Hello,
>>
>> (cc'ing i915 folks)
>>
>> On Wed, Aug 30, 2023 at 04:57:42PM +0200, Heiner Kallweit wrote:
>>> Recently I started to see the following warning on linux-next and presumably
>>> this may be related to the refactoring of the workqueue core code.
>>>
>>> [ 56.900223] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
>>> for >1us 4 times, consider switching to WQ_UNBOUND
>>> [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
>>> >1us 4 times, consider switching to WQ_UNBOUND
>>> [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
>>> for >1us 8 times, consider switching to WQ_UNBOUND
>>> [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
>>> >1us 8 times, consider switching to WQ_UNBOUND
>>>
>>> Adding WQ_UNBOUND to these queues didn't change the behavior.
>>
>> That should have made them go away as the code path isn't active at all for
>> WQ_UNBOUND workqueues. Can you please double check?
>>
>>> Maybe relevant: I run the affected system headless.
>>
>> i915 folks, workqueue recently added debug warnings which trigger when a
>> per-cpu work item hogs the CPU for too long - 10ms in this case. This is
>> problematic because such work item can stall other per-cpu work items.
>>
>> * Is it expected for the above two work functions to occupy the CPU for over
>> 10ms repeatedly?
>
> No, this shouldn't happen.
>
> I assume it happens in
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>
> after cfd48ad8c4a9 ("drm/i915: Fix HPD polling, reenabling the output poll
> work as needed")
>
> which could result in the above problem.
>
> Could you give a try to
> https://lore.kernel.org/all/20230809104307.1218058-1-imre.d...@intel.com/
>
> and if that doesn't help provide more information/logs, by opening a
> ticket at:
> https://gitlab.freedesktop.org/drm/intel/-/issues/new
>
Done
https://gitlab.freedesktop.org/drm/intel/-/issues/9245
> Thanks,
> Imre
>
>> * If so, can we make them use an unbound workqueue instead?
>>
>> Thanks.
>>
>> --
>> tejun
Re: [Intel-gfx] WQ_UNBOUND warning since recent workqueue refactoring
On Wed, Aug 30, 2023 at 07:51:13AM -1000, Tejun Heo wrote:
Hi,
> Hello,
>
> (cc'ing i915 folks)
>
> On Wed, Aug 30, 2023 at 04:57:42PM +0200, Heiner Kallweit wrote:
> > Recently I started to see the following warning on linux-next and presumably
> > this may be related to the refactoring of the workqueue core code.
> >
> > [ 56.900223] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
> > for >1us 4 times, consider switching to WQ_UNBOUND
> > [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
> > >1us 4 times, consider switching to WQ_UNBOUND
> > [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU
> > for >1us 8 times, consider switching to WQ_UNBOUND
> > [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for
> > >1us 8 times, consider switching to WQ_UNBOUND
> >
> > Adding WQ_UNBOUND to these queues didn't change the behavior.
>
> That should have made them go away as the code path isn't active at all for
> WQ_UNBOUND workqueues. Can you please double check?
>
> > Maybe relevant: I run the affected system headless.
>
> i915 folks, workqueue recently added debug warnings which trigger when a
> per-cpu work item hogs the CPU for too long - 10ms in this case. This is
> problematic because such work item can stall other per-cpu work items.
>
> * Is it expected for the above two work functions to occupy the CPU for over
> 10ms repeatedly?
No, this shouldn't happen.
I assume it happens in
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
after cfd48ad8c4a9 ("drm/i915: Fix HPD polling, reenabling the output poll work
as needed")
which could result in the above problem.
Could you give a try to
https://lore.kernel.org/all/20230809104307.1218058-1-imre.d...@intel.com/
and if that doesn't help provide more information/logs, by opening a
ticket at:
https://gitlab.freedesktop.org/drm/intel/-/issues/new
Thanks,
Imre
> * If so, can we make them use an unbound workqueue instead?
>
> Thanks.
>
> --
> tejun
Re: [Intel-gfx] WQ_UNBOUND warning since recent workqueue refactoring
Hello, (cc'ing i915 folks) On Wed, Aug 30, 2023 at 04:57:42PM +0200, Heiner Kallweit wrote: > Recently I started to see the following warning on linux-next and presumably > this may be related to the refactoring of the workqueue core code. > > [ 56.900223] workqueue: output_poll_execute [drm_kms_helper] hogged CPU for > >1us 4 times, consider switching to WQ_UNBOUND > [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for > >1us 4 times, consider switching to WQ_UNBOUND > [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU for > >1us 8 times, consider switching to WQ_UNBOUND > [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for > >1us 8 times, consider switching to WQ_UNBOUND > > Adding WQ_UNBOUND to these queues didn't change the behavior. That should have made them go away as the code path isn't active at all for WQ_UNBOUND workqueues. Can you please double check? > Maybe relevant: I run the affected system headless. i915 folks, workqueue recently added debug warnings which trigger when a per-cpu work item hogs the CPU for too long - 10ms in this case. This is problematic because such work item can stall other per-cpu work items. * Is it expected for the above two work functions to occupy the CPU for over 10ms repeatedly? * If so, can we make them use an unbound workqueue instead? Thanks. -- tejun
