drm/i915: Add unit tests for the breadcrumb rbtree, wakeups

Third retroactive test, make sure that the seqno waiters are woken.

v2: Smattering of comments, rearrange code
v3: Fix IDLE assert to avoid startup/sleep races

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170213171558.20942-5-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c b/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
index 32a27e5..d1b99b5 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/selftests/intel_breadcrumbs.c
@@ -259,11 +259,212 @@ out_engines:
        return err;
 }
 
+struct igt_wakeup {
+       struct task_struct *tsk;
+       atomic_t *ready, *set, *done;
+       struct intel_engine_cs *engine;
+       unsigned long flags;
+#define STOP 0
+#define IDLE 1
+       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 bool wait_for_ready(struct igt_wakeup *w)
+{
+       DEFINE_WAIT(ready);
+
+       set_bit(IDLE, &w->flags);
+       if (atomic_dec_and_test(w->done))
+               wake_up_atomic_t(w->done);
+
+       if (test_bit(STOP, &w->flags))
+               goto out;
+
+       for (;;) {
+               prepare_to_wait(w->wq, &ready, TASK_INTERRUPTIBLE);
+               if (atomic_read(w->ready) == 0)
+                       break;
+
+               schedule();
+       }
+       finish_wait(w->wq, &ready);
+
+out:
+       clear_bit(IDLE, &w->flags);
+       if (atomic_dec_and_test(w->set))
+               wake_up_atomic_t(w->set);
+
+       return !test_bit(STOP, &w->flags);
+}
+
+static int igt_wakeup_thread(void *arg)
+{
+       struct igt_wakeup *w = arg;
+       struct intel_wait wait;
+
+       while (wait_for_ready(w)) {
+               GEM_BUG_ON(kthread_should_stop());
+
+               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;
+
+                       if (test_bit(STOP, &w->flags)) /* emergency escape */
+                               break;
+
+                       schedule();
+               }
+               intel_engine_remove_wait(w->engine, &wait);
+               __set_current_state(TASK_RUNNING);
+       }
+
+       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(ready, 0);
+       wake_up_all(wq);
+
+       wait_on_atomic_t(set, wait_atomic, TASK_UNINTERRUPTIBLE);
+       atomic_set(ready, count);
+       atomic_set(done, count);
+}
+
+static int igt_wakeup(void *arg)
+{
+       I915_RND_STATE(prng);
+       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 = BIT(IDLE);
+
+               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;
+
+               /* The waiter threads start paused as we assign them a random
+                * seqno and reset the engine. Once the engine is reset,
+                * we signal that the threads may begin their wait upon their
+                * seqno.
+                */
+               for (n = 0; n < count; n++) {
+                       GEM_BUG_ON(!test_bit(IDLE, &waiters[n].flags));
+                       waiters[n].seqno =
+                               1 + prandom_u32_state(&prng) % max_seqno;
+               }
+               mock_seqno_advance(engine, 0);
+               igt_wake_all_sync(&ready, &set, &done, &wq, count);
+
+               /* Simulate the GPU doing chunks of work, with one or more
+                * seqno appearing to finish at the same time. A random number
+                * of threads will be waiting upon the update and hopefully be
+                * woken.
+                */
+               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);
+
+               /* With the seqno now beyond any of the waiting threads, they
+                * should all be woken, see that they are complete and signal
+                * that they are ready for the next test. We wait until all
+                * threads are complete and waiting for us (i.e. not a 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(STOP, &waiters[n].flags);
+       }
+       mock_seqno_advance(engine, INT_MAX); /* wakeup any broken waiters */
+       igt_wake_all_sync(&ready, &set, &done, &wq, n);
+
+       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;