On Sat, Sep 30, 2023 at 03:48:07PM -0400, Luben Tuikov wrote: > On 2023-09-29 17:53, Luben Tuikov wrote: > > Hi, > > > > On 2023-09-19 01:01, Matthew Brost wrote: > >> If the TDR is set to a very small value it can fire before the > >> submission is started in the function drm_sched_start. The submission is > >> expected to running when the TDR fires, fix this ordering so this > >> expectation is always met. > >> > >> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> > >> --- > >> drivers/gpu/drm/scheduler/sched_main.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c > >> index 09ef07b9e9d5..a5cc9b6c2faa 100644 > >> --- a/drivers/gpu/drm/scheduler/sched_main.c > >> +++ b/drivers/gpu/drm/scheduler/sched_main.c > >> @@ -684,10 +684,10 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery) > >> drm_sched_job_done(s_job, -ECANCELED); > >> } > >> > >> + drm_sched_submit_start(sched); > >> + > >> if (full_recovery) > >> drm_sched_start_timeout_unlocked(sched); > >> - > >> - drm_sched_submit_start(sched); > >> } > >> EXPORT_SYMBOL(drm_sched_start); > > > > No. > > I don't think we will ever agree on this but I pulled out this patch and the next in Xe. It seems to work without these changes, I believe understand why and think it should actually work without this change. If for some reason it didn't work, I know how I can work around this in the Xe submission backend. With this, I will drop these in the next rev. But more on why I disagree below... > > A timeout timer should be started before we submit anything down to the hardware. > > See Message-ID: <ed3aca10-8a9f-4698-92f4-21558fa6cfe3@xxxxxxx>, > > and Message-ID: <8e5eab14-9e55-42c9-b6ea-02fcc591266d@xxxxxxx>. > > > > You shouldn't start TDR at an arbitrarily late time after job > > submission to the hardware. To close this, the timer is started > > before jobs are submitted to the hardware. > > > > One possibility is to increase the timeout timer value. No matter what the timeout value is there will always be a race of TDR firing before run_job() is called. > > If we went with this general change as we see here and in the subsequent patch--starting > the TDR _after_ submitting jobs for execution to the hardware--this is what generally happens, > 1. submit one or many jobs for execution; > 2. one or many jobs may execute, complete, hang, etc.; > 3. at some arbitrary time in the future, start TDR. > Which means that the timeout doesn't necessarily track the time allotted for a job to finish > executing in the hardware. It ends up larger than intended. Yes, conversely it can be smaller the way it is coded now. Kinda just a matter of opinion on which one to prefer. Matt > -- > Regards, > Luben >
