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? > > > 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.deak@xxxxxxxxx/ 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
