On Fri, Sep 13, 2024 at 10:03 AM Michel Dänzer <michel.daenzer@xxxxxxxxxxx> wrote: > > On 2024-09-13 18:53, Rob Clark wrote: > > From: Rob Clark <robdclark@xxxxxxxxxxxx> > > > > Fixes a race condition reported here: https://github.com/AsahiLinux/linux/issues/309#issuecomment-2238968609 > > > > The whole premise of lockless access to a single-producer-single- > > consumer queue is that there is just a single producer and single > > consumer. That means we can't call drm_sched_can_queue() (which is > > about queueing more work to the hw, not to the spsc queue) from > > anywhere other than the consumer (wq). > > > > This call in the producer is just an optimization to avoid scheduling > > the consuming worker if it cannot yet queue more work to the hw. It > > is safe to drop this optimization to avoid the race condition. > > > > Suggested-by: Asahi Lina <lina@xxxxxxxxxxxxx> > > Fixes: a78422e9dff3 ("drm/sched: implement dynamic job-flow control") > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx> > > --- > > drivers/gpu/drm/scheduler/sched_main.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c > > index ab53ab486fe6..1af1dbe757d5 100644 > > --- a/drivers/gpu/drm/scheduler/sched_main.c > > +++ b/drivers/gpu/drm/scheduler/sched_main.c > > @@ -1020,8 +1020,7 @@ EXPORT_SYMBOL(drm_sched_job_cleanup); > > void drm_sched_wakeup(struct drm_gpu_scheduler *sched, > > struct drm_sched_entity *entity) > > { > > - if (drm_sched_can_queue(sched, entity)) > > - drm_sched_run_job_queue(sched); > > + drm_sched_run_job_queue(sched); > > } > > > > /** > > The entity parameter is unused now. Right.. and we probably should collapse drm_sched_wakeup() and drm_sched_run_job_queue().. But this fix needs to be cherry picked back to a bunch of release branches, so I intentionally avoided refactoring as part of the fix. BR, -R > > > -- > Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer > https://redhat.com \ Libre software enthusiast
