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