| Message ID | 20191009094456.9704-1-steven.price@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] drm/panfrost: Handle resetting on timeout better | expand |
On Wed, Oct 9, 2019 at 4:45 AM Steven Price <steven.price@arm.com> wrote: > > Panfrost uses multiple schedulers (one for each slot, so 2 in reality), > and on a timeout has to stop all the schedulers to safely perform a > reset. However more than one scheduler can trigger a timeout at the same > time. This race condition results in jobs being freed while they are > still in use. > > When stopping other slots use cancel_delayed_work_sync() to ensure that > any timeout started for that slot has completed. Also use > mutex_trylock() to obtain reset_lock. This means that only one thread > attempts the reset, the other threads will simply complete without doing > anything (the first thread will wait for this in the call to > cancel_delayed_work_sync()). > > While we're here and since the function is already dependent on > sched_job not being NULL, let's remove the unnecessary checks. > > Fixes: aa20236784ab ("drm/panfrost: Prevent concurrent resets") > Tested-by: Neil Armstrong <narmstrong@baylibre.com> > Signed-off-by: Steven Price <steven.price@arm.com> > --- > v2: > * Added fixes and tested-by tags > * Moved cleanup of panfrost_core_dump() comment to separate patch > > drivers/gpu/drm/panfrost/panfrost_job.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) Both patches applied. Rob
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c index a58551668d9a..21f34d44aac2 100644 --- a/drivers/gpu/drm/panfrost/panfrost_job.c +++ b/drivers/gpu/drm/panfrost/panfrost_job.c @@ -381,13 +381,19 @@ static void panfrost_job_timedout(struct drm_sched_job *sched_job) job_read(pfdev, JS_TAIL_LO(js)), sched_job); - mutex_lock(&pfdev->reset_lock); + if (!mutex_trylock(&pfdev->reset_lock)) + return; - for (i = 0; i < NUM_JOB_SLOTS; i++) - drm_sched_stop(&pfdev->js->queue[i].sched, sched_job); + for (i = 0; i < NUM_JOB_SLOTS; i++) { + struct drm_gpu_scheduler *sched = &pfdev->js->queue[i].sched; + + drm_sched_stop(sched, sched_job); + if (js != i) + /* Ensure any timeouts on other slots have finished */ + cancel_delayed_work_sync(&sched->work_tdr); + } - if (sched_job) - drm_sched_increase_karma(sched_job); + drm_sched_increase_karma(sched_job); spin_lock_irqsave(&pfdev->js->job_lock, flags); for (i = 0; i < NUM_JOB_SLOTS; i++) {
Panfrost uses multiple schedulers (one for each slot, so 2 in reality), and on a timeout has to stop all the schedulers to safely perform a reset. However more than one scheduler can trigger a timeout at the same time. This race condition results in jobs being freed while they are still in use. When stopping other slots use cancel_delayed_work_sync() to ensure that any timeout started for that slot has completed. Also use mutex_trylock() to obtain reset_lock. This means that only one thread attempts the reset, the other threads will simply complete without doing anything (the first thread will wait for this in the call to cancel_delayed_work_sync()). While we're here and since the function is already dependent on sched_job not being NULL, let's remove the unnecessary checks. Fixes: aa20236784ab ("drm/panfrost: Prevent concurrent resets") Tested-by: Neil Armstrong <narmstrong@baylibre.com> Signed-off-by: Steven Price <steven.price@arm.com> --- v2: * Added fixes and tested-by tags * Moved cleanup of panfrost_core_dump() comment to separate patch drivers/gpu/drm/panfrost/panfrost_job.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)