On 4/13/22 01:59, Erico Nunes wrote:
On Tue, Apr 12, 2022 at 9:41 PM Andrey Grodzovsky andrey.grodzovsky@amd.com wrote:
On 2022-04-12 14:20, Dmitry Osipenko wrote:
On 4/12/22 19:51, Andrey Grodzovsky wrote:
On 2022-04-11 18:15, Dmitry Osipenko wrote:
Interrupt context can't sleep. Drivers like Panfrost and MSM are taking mutex when job is released, and thus, that code can sleep. This results into "BUG: scheduling while atomic" if locks are contented while job is freed. There is no good reason for releasing scheduler's jobs in IRQ context, hence use normal context to fix the trouble.
I am not sure this is the beast Idea to leave job's sw fence signalling to be executed in system_wq context which is prone to delays of executing various work items from around the system. Seems better to me to leave the fence signaling within the IRQ context and offload only the job freeing or, maybe handle rescheduling to thread context within drivers implemention of .free_job cb. Not really sure which is the better.
We're talking here about killing jobs when driver destroys context, which doesn't feel like it needs to be a fast path. I could move the signalling into drm_sched_entity_kill_jobs_cb() and use unbound wq, but do we really need this for a slow path?
You can't move the signaling back to drm_sched_entity_kill_jobs_cb since this will bring back the lockdep splat that 'drm/sched: Avoid lockdep spalt on killing a processes' was fixing.
I see your point and i guess we can go this way too. Another way would be to add to panfrost and msm job a work_item and reschedule to thread context from within their .free_job callbacks but that probably to cumbersome to be justified here.
FWIW since this mentioned individual drivers, commit 'drm/sched: Avoid lockdep spalt on killing a processes' also introduced problems for lima. There were some occurrences in our CI https://gitlab.freedesktop.org/mesa/mesa/-/jobs/20980982/raw . Later I found it also reproducible on normal usage when just closing applications, so it may be affecting users too.
I tested this patch and looks like it fixes things for lima.
This patch indeed should fix that lima bug. Feel free to give yours tested-by :)