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 >10000us 4 times, consider switching to WQ_UNBOUND >>> [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for >>> >10000us 4 times, consider switching to WQ_UNBOUND >>> [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU >>> for >10000us 8 times, consider switching to WQ_UNBOUND >>> [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for >>> >10000us 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
