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drm/panfrost: Handle resetting on timeout better

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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: aa20236784 ("drm/panfrost: Prevent concurrent resets")
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191009094456.9704-1-steven.price@arm.com
This commit is contained in:
Steven Price 2019-10-09 10:44:55 +01:00 committed by Rob Herring
parent 603e398a3d
commit de89212ddb
1 changed files with 11 additions and 5 deletions
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16
drivers/gpu/drm/panfrost/panfrost_job.c
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@ -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;
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);
spin_lock_irqsave(&pfdev->js->job_lock, flags);
for (i = 0; i < NUM_JOB_SLOTS; i++) {