On Mon, 2025-03-10 at 09:55 +0000, Tvrtko Ursulin wrote: > > On 07/03/2025 18:06, Philipp Stanner wrote: > > On Fri, 2025-03-07 at 16:59 +0000, Tvrtko Ursulin wrote: > > > > > > On 07/03/2025 13:41, Philipp Stanner wrote: > > > > Hi, > > > > > > > > You forgot to put folks in CC as recipents for the cover letter > > > > :( > > > > > > > > > > > > On Thu, 2025-03-06 at 17:05 +0000, Tvrtko Ursulin wrote: > > > > > Move some options out into a new debug specific kconfig file > > > > > in > > > > > order > > > > > to > > > > > make things a bit cleaner. > > > > > > > > > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx> > > > > > Cc: Christian König <christian.koenig@xxxxxxx> > > > > > Cc: Danilo Krummrich <dakr@xxxxxxxxxx> > > > > > Cc: Matthew Brost <matthew.brost@xxxxxxxxx> > > > > > Cc: Philipp Stanner <phasta@xxxxxxxxxx> > > > > > > > > We all have our individual work flows, so don't take this as > > > > lecturing > > > > or anything – I just suspect that I was forgotten in the cover > > > > letter > > > > because you Cc people by hand in the individual patches. > > > > > > > > What I do is that I run get_maintainer and then put the > > > > individuals > > > > listed there into the --to= field. That sends the entire series > > > > to > > > > all > > > > of them. > > > > > > > > Only sometimes, when there's a huge list of recipents or when > > > > the > > > > patches of a series are very independent, I deviate from that > > > > rule. > > > > > > > > JFYI > > > > > > Notice it was there in v3, I just omitted to paste it this time. > > > > > > > Anyways, we have a bigger problem about the entire series. I > > > > now > > > > tested > > > > again with the same setup as yesterday and the faults are > > > > indeed > > > > gone, > > > > so that's good. > > > > > > > > But to be sure I then did run kmemleak and got a list of leaks > > > > that > > > > is > > > > more than 2000 lines long. > > > > > > There is this comment for drm_sched_fini which ends with: > > > > > > """ > > > ... > > > * This stops submission of new jobs to the hardware through > > > * drm_sched_backend_ops.run_job(). Consequently, > > > drm_sched_backend_ops.free_job() > > > * will not be called for all jobs still in > > > drm_gpu_scheduler.pending_list. > > > * There is no solution for this currently. Thus, it is up to > > > the > > > driver to make > > > * sure that: > > > * > > > * a) drm_sched_fini() is only called after for all submitted > > > jobs > > > * drm_sched_backend_ops.free_job() has been called or that > > > * b) the jobs for which drm_sched_backend_ops.free_job() has > > > not > > > been > > > called > > > * after drm_sched_fini() ran are freed manually. > > > * > > > > > > * FIXME: Take care of the above problem and prevent this > > > function > > > from > > > leaking > > > * the jobs in drm_gpu_scheduler.pending_list under any > > > circumstances. > > > """ > > > > > > I got bitten by that. Keep forgetting how fragile the thing is.. > > > :( > > > > argh damn, those are *all* from the pending_list?! > > Right, all leaks I saw were from the drm_sched_basic_entity_cleanup > test. All other tests actually wait for jobs to finish so can't hit > that. > > Fix was simply to add a drm_sched_job_cleanup call when unwinding > unfinished mock scheduler jobs from drm_mock_sched_fini, which > happens > before calling drm_sched_fini. > > That's pretty much how things are expected to be handled AFAIU. > > > OK. Well. > > > > Now we've got a philosophical problem: > > > > We still have to fix those leaks (I'm still working on it, but my > > current attempt has failed and I probably fall back to a refcount > > solution). > > You propose to move the responsibility of cleaning up in-flight jobs > to > the scheduler core? The scheduler core is already and has always been responsible for cleaning up "in-flight jobs". It does so through backend_ops.free_job(). And we prevent it from cleaning up all jobs by cancelling the work items in drm_sched_fini(). Semantically, the scheduler is the one in charge of the job life times. As of right now, every single driver is effectively forced to implement the same logic, but they have implemented it in different ways (Xe refcounts the scheduler and only calls drm_sched_fini() once refcnt == 0, Nouveau maintains a copy of the pending_list, blocking for it to become empty before calling drm_sched_fini()) > > > And to see whether the fix actually fixes the leaks, directly using > > the > > kunit tests would be handy. > > > > After all, this is what the kunit tests are there for: show what is > > broken within the scheduler. And those leaks definitely qualify. Or > > should kunit tests follow the same rules we demand from drivers? > > > > I'd like to hear more opinions about that. > > > > @Danilo, @Dave, @Sima > > would it be OK if we add kunit tests for the scheduler to DRM that > > cause leaks until we can fix them? > > It is indeed a bit philosophical. I'd say only if there is a 100% > agreement that drm_sched_fini should be able to clean up, or drive > cleaning up, all driver state. And if we are prepared to handle a > permanently failing test from now to some future date when this would > be > implemented. > > I have a similar conundrum with set priority, where I was > contemplating > to add a permanently failing test showing how that does not fully > work, > and then get improved with my deadline scheduling series. > > On the other side of the argument is the past experience of CI > systems > generally not coping well with permanently failing test. Eventually > they > succumb to the pressure to remove them due noisy results. Therefore > other option is to have the mock scheduler adhere to the current > implementation and only change it once the DRM scheduler rules > change. Can you think of a way, like flags or kconfig options, with which developers such as you and I could "switch the bugs on" for working on those issues? P. > > Regards, > > Tvrtko >
