On Thu, Mar 17, 2022 at 9:45 AM Christian König <christian.koenig@xxxxxxx> wrote: > > Am 17.03.22 um 17:18 schrieb Rob Clark: > > On Thu, Mar 17, 2022 at 9:04 AM Christian König > > <christian.koenig@xxxxxxx> 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. we don't wait on fences in shrinker, only purging or evicting things that are already ready. Actually, waiting on fences in shrinker path sounds like a pretty bad idea. > 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. yeah, it would work to drain the scheduler.. I guess that might be the more portable approach as far as generic solution for suspend. BR, -R > 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 > >>> >
