[Intel-gfx] [PATCH 06/37] drm/i915: Add unit tests for the breadcrumb rbtree, wakeups

[Tvrtko Ursulin]

On 11/01/2017 21:09, Chris Wilson wrote:
> Third retroactive test, make sure that the seqno waiters are woken.

There are some open questions from the previous round (early December), 
not least of which is that I think we really need good comments in 
tests. Especially ones like this one which is pretty advanced. We need 
an overall description and some commentary on the stages. It is not 
straightforward to reverse engineer this, so doing it every time this 
code will need some attention for one reason or the other will be a PITA.

Regards,

Tvrtko

>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c | 171 +++++++++++++++++++++
>  1 file changed, 171 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c b/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
> index e9dff6eee323..bee86470a91d 100644
> --- a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
> @@ -263,11 +263,182 @@ static int igt_insert_complete(void *arg)
>  	return err;
>  }
>
> +struct igt_wakeup {
> +	struct task_struct *tsk;
> +	atomic_t *ready, *set, *done;
> +	struct intel_engine_cs *engine;
> +	unsigned long flags;
> +	wait_queue_head_t *wq;
> +	u32 seqno;
> +};
> +
> +static int wait_atomic(atomic_t *p)
> +{
> +	schedule();
> +	return 0;
> +}
> +
> +static int wait_atomic_timeout(atomic_t *p)
> +{
> +	return schedule_timeout(10 * HZ) ? 0 : -ETIMEDOUT;
> +}
> +
> +static int igt_wakeup_thread(void *arg)
> +{
> +	struct igt_wakeup *w = arg;
> +	struct intel_wait wait;
> +
> +	while (!kthread_should_stop()) {
> +		DEFINE_WAIT(ready);
> +
> +		for (;;) {
> +			prepare_to_wait(w->wq, &ready, TASK_INTERRUPTIBLE);
> +			if (atomic_read(w->ready) == 0)
> +				break;
> +
> +			schedule();
> +		}
> +		finish_wait(w->wq, &ready);
> +		if (atomic_dec_and_test(w->set))
> +			wake_up_atomic_t(w->set);
> +
> +		if (test_bit(0, &w->flags))
> +			break;
> +
> +		intel_wait_init(&wait, w->seqno);
> +		intel_engine_add_wait(w->engine, &wait);
> +		for (;;) {
> +			set_current_state(TASK_UNINTERRUPTIBLE);
> +			if (i915_seqno_passed(intel_engine_get_seqno(w->engine),
> +					      w->seqno))
> +				break;
> +
> +			schedule();
> +		}
> +		intel_engine_remove_wait(w->engine, &wait);
> +		__set_current_state(TASK_RUNNING);
> +
> +		if (atomic_dec_and_test(w->done))
> +			wake_up_atomic_t(w->done);
> +	}
> +
> +	if (atomic_dec_and_test(w->done))
> +		wake_up_atomic_t(w->done);
> +	return 0;
> +}
> +
> +static void igt_wake_all_sync(atomic_t *ready,
> +			      atomic_t *set,
> +			      atomic_t *done,
> +			      wait_queue_head_t *wq,
> +			      int count)
> +{
> +	atomic_set(set, count);
> +	atomic_set(done, count);
> +
> +	atomic_set(ready, 0);
> +	wake_up_all(wq);
> +
> +	wait_on_atomic_t(set, wait_atomic, TASK_UNINTERRUPTIBLE);
> +	atomic_set(ready, count);
> +}
> +
> +static int igt_wakeup(void *arg)
> +{
> +	const int state = TASK_UNINTERRUPTIBLE;
> +	struct intel_engine_cs *engine = arg;
> +	struct igt_wakeup *waiters;
> +	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
> +	const int count = 4096;
> +	const u32 max_seqno = count / 4;
> +	atomic_t ready, set, done;
> +	int err = -ENOMEM;
> +	int n, step;
> +
> +	mock_engine_reset(engine);
> +
> +	waiters = drm_malloc_gfp(count, sizeof(*waiters), GFP_TEMPORARY);
> +	if (!waiters)
> +		goto out_engines;
> +
> +	/* Create a large number of threads, each waiting on a random seqno.
> +	 * Multiple waiters will be waiting for the same seqno.
> +	 */
> +	atomic_set(&ready, count);
> +	for (n = 0; n < count; n++) {
> +		waiters[n].wq = &wq;
> +		waiters[n].ready = &ready;
> +		waiters[n].set = &set;
> +		waiters[n].done = &done;
> +		waiters[n].engine = engine;
> +		waiters[n].flags = 0;
> +
> +		waiters[n].tsk = kthread_run(igt_wakeup_thread, &waiters[n],
> +					     "i915/igt:%d", n);
> +		if (IS_ERR(waiters[n].tsk))
> +			goto out_waiters;
> +
> +		get_task_struct(waiters[n].tsk);
> +	}
> +
> +	for (step = 1; step <= max_seqno; step <<= 1) {
> +		u32 seqno;
> +
> +		for (n = 0; n < count; n++)
> +			waiters[n].seqno = 1 + get_random_int() % max_seqno;
> +
> +		mock_seqno_advance(engine, 0);
> +		igt_wake_all_sync(&ready, &set, &done, &wq, count);
> +
> +		for (seqno = 1; seqno <= max_seqno + step; seqno += step) {
> +			usleep_range(50, 500);
> +			mock_seqno_advance(engine, seqno);
> +		}
> +		GEM_BUG_ON(intel_engine_get_seqno(engine) < 1 + max_seqno);
> +
> +		err = wait_on_atomic_t(&done, wait_atomic_timeout, state);
> +		if (err) {
> +			pr_err("Timed out waiting for %d remaining waiters\n",
> +			       atomic_read(&done));
> +			break;
> +		}
> +
> +		err = check_rbtree_empty(engine);
> +		if (err)
> +			break;
> +	}
> +
> +out_waiters:
> +	for (n = 0; n < count; n++) {
> +		if (IS_ERR(waiters[n].tsk))
> +			break;
> +
> +		set_bit(0, &waiters[n].flags);
> +	}
> +
> +	igt_wake_all_sync(&ready, &set, &done, &wq, n);
> +	wait_on_atomic_t(&done, wait_atomic, state);
> +
> +	for (n = 0; n < count; n++) {
> +		if (IS_ERR(waiters[n].tsk))
> +			break;
> +
> +		kthread_stop(waiters[n].tsk);
> +		put_task_struct(waiters[n].tsk);
> +	}
> +
> +	drm_free_large(waiters);
> +out_engines:
> +	mock_engine_flush(engine);
> +	return err;
> +}
> +
>  int intel_breadcrumbs_mock_selftests(void)
>  {
>  	static const struct i915_subtest tests[] = {
>  		SUBTEST(igt_random_insert_remove),
>  		SUBTEST(igt_insert_complete),
> +		SUBTEST(igt_wakeup),
>  	};
>  	struct intel_engine_cs *engine;
>  	int err;
>