From: Steven Price <steven.price@xxxxxxx>
commit 5b3ec8134f5f9fa1ed0a538441a495521078bbee upstream.
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@xxxxxxxxxxxx>
Signed-off-by: Steven Price <steven.price@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20191009094456.9704-1-steven.price@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/panfrost/panfrost_job.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -384,13 +384,19 @@ static void panfrost_job_timedout(struct
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;
- if (sched_job)
- drm_sched_increase_karma(sched_job);
+ drm_sched_stop(sched, sched_job);
+ if (js != i)
+ /* Ensure any timeouts on other slots have finished */
+ cancel_delayed_work_sync(&sched->work_tdr);
+ }
+
+ drm_sched_increase_karma(sched_job);
/* panfrost_core_dump(pfdev); */
