Messages in this thread | | | Date | Thu, 17 Mar 2022 17:44:57 +0100 | Subject | Re: [PATCH 2/3] drm/msm/gpu: Park scheduler threads for system suspend | From | Christian König <> |
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Am 17.03.22 um 17:18 schrieb Rob Clark: > On Thu, Mar 17, 2022 at 9:04 AM Christian König > <christian.koenig@amd.com> wrote: >> Am 17.03.22 um 16:10 schrieb Rob Clark: >>> [SNIP] >>> userspace frozen != kthread frozen .. that is what this patch is >>> trying to address, so we aren't racing between shutting down the hw >>> and the scheduler shoveling more jobs at us. >> Well exactly that's the problem. The scheduler is supposed to shoveling >> more jobs at us until it is empty. >> >> Thinking more about it we will then keep some dma_fence instance >> unsignaled and that is and extremely bad idea since it can lead to >> deadlocks during suspend. > Hmm, perhaps that is true if you need to migrate things out of vram? > It is at least not a problem when vram is not involved.
No, it's much wider than that.
See what can happen is that the memory management shrinkers want to wait for a dma_fence during suspend.
And if you stop the scheduler they will just wait forever.
What you need to do instead is to drain the scheduler, e.g. call drm_sched_entity_flush() with a proper timeout for each entity you have created.
Regards, Christian.
> >> So this patch here is an absolute clear NAK from my side. If amdgpu is >> doing something similar that is a severe bug and needs to be addressed >> somehow. > I think amdgpu's use of kthread_park is not related to suspend, but > didn't look too closely. > > And perhaps the solution for this problem is more complex in the case > of amdgpu, I'm not super familiar with the constraints there. But I > think it is a fine solution for integrated GPUs. > > BR, > -R > >> Regards, >> Christian. >> >>> BR, >>> -R >>>
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