drm/i915/selftests: Stop using kthread_stop()

Since a7c01fa93aeb ("signal: break out of wait loops on kthread_stop()")
kthread_stop() started asserting a pending signal which wreaks havoc with
a few of our selftests. Mainly because they are not fully expecting to
handle signals, but also cutting the intended test runtimes short due
signal_pending() now returning true (via __igt_timeout), which therefore
breaks both the patterns of:

  kthread_run()
  ..sleep for igt_timeout_ms to allow test to exercise stuff..
  kthread_stop()

And check for errors recorded in the thread.

And also:

    Main thread  |   Test thread
  ---------------+------------------------------
  kthread_run()  |
  kthread_stop() |  do stuff until __igt_timeout
		 |  -- exits early due signal --

Where this kthread_stop() was assume would have a "join" semantics, which
it would have had if not the new signal assertion issue.

To recap, threads are now likely to catch a previously impossible
ERESTARTSYS or EINTR, marking the test as failed, or have a pointlessly
short run time.

To work around this start using kthread_work(er) API which provides
an explicit way of waiting for threads to exit. And for cases where
parent controls the test duration we add explicit signaling which threads
will now use instead of relying on kthread_should_stop().

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221020130841.3845791-1-tvrtko.ursulin@linux.intel.com

1 files changed, 162 insertions, 90 deletions

diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 818a4909c1f3..a46350c37e9d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -299,9 +299,18 @@ __live_request_alloc(struct intel_context *ce)
 	return intel_context_create_request(ce);
 }
 
-static int __igt_breadcrumbs_smoketest(void *arg)
+struct smoke_thread {
+	struct kthread_worker *worker;
+	struct kthread_work work;
+	struct smoketest *t;
+	bool stop;
+	int result;
+};
+
+static void __igt_breadcrumbs_smoketest(struct kthread_work *work)
 {
-	struct smoketest *t = arg;
+	struct smoke_thread *thread = container_of(work, typeof(*thread), work);
+	struct smoketest *t = thread->t;
 	const unsigned int max_batch = min(t->ncontexts, t->max_batch) - 1;
 	const unsigned int total = 4 * t->ncontexts + 1;
 	unsigned int num_waits = 0, num_fences = 0;
@@ -320,8 +329,10 @@ static int __igt_breadcrumbs_smoketest(void *arg)
 	 */
 
 	requests = kcalloc(total, sizeof(*requests), GFP_KERNEL);
-	if (!requests)
-		return -ENOMEM;
+	if (!requests) {
+		thread->result = -ENOMEM;
+		return;
+	}
 
 	order = i915_random_order(total, &prng);
 	if (!order) {
@@ -329,7 +340,7 @@ static int __igt_breadcrumbs_smoketest(void *arg)
 		goto out_requests;
 	}
 
-	while (!kthread_should_stop()) {
+	while (!READ_ONCE(thread->stop)) {
 		struct i915_sw_fence *submit, *wait;
 		unsigned int n, count;
 
@@ -437,7 +448,7 @@ static int __igt_breadcrumbs_smoketest(void *arg)
 	kfree(order);
 out_requests:
 	kfree(requests);
-	return err;
+	thread->result = err;
 }
 
 static int mock_breadcrumbs_smoketest(void *arg)
@@ -450,7 +461,7 @@ static int mock_breadcrumbs_smoketest(void *arg)
 		.request_alloc = __mock_request_alloc
 	};
 	unsigned int ncpus = num_online_cpus();
-	struct task_struct **threads;
+	struct smoke_thread *threads;
 	unsigned int n;
 	int ret = 0;
 
@@ -479,28 +490,37 @@ static int mock_breadcrumbs_smoketest(void *arg)
 	}
 
 	for (n = 0; n < ncpus; n++) {
-		threads[n] = kthread_run(__igt_breadcrumbs_smoketest,
-					 &t, "igt/%d", n);
-		if (IS_ERR(threads[n])) {
-			ret = PTR_ERR(threads[n]);
+		struct kthread_worker *worker;
+
+		worker = kthread_create_worker(0, "igt/%d", n);
+		if (IS_ERR(worker)) {
+			ret = PTR_ERR(worker);
 			ncpus = n;
 			break;
 		}
 
-		get_task_struct(threads[n]);
+		threads[n].worker = worker;
+		threads[n].t = &t;
+		threads[n].stop = false;
+		threads[n].result = 0;
+
+		kthread_init_work(&threads[n].work,
+				  __igt_breadcrumbs_smoketest);
+		kthread_queue_work(worker, &threads[n].work);
 	}
 
-	yield(); /* start all threads before we begin */
 	msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
 
 	for (n = 0; n < ncpus; n++) {
 		int err;
 
-		err = kthread_stop(threads[n]);
+		WRITE_ONCE(threads[n].stop, true);
+		kthread_flush_work(&threads[n].work);
+		err = READ_ONCE(threads[n].result);
 		if (err < 0 && !ret)
 			ret = err;
 
-		put_task_struct(threads[n]);
+		kthread_destroy_worker(threads[n].worker);
 	}
 	pr_info("Completed %lu waits for %lu fence across %d cpus\n",
 		atomic_long_read(&t.num_waits),
@@ -1419,9 +1439,18 @@ out_free:
 	return err;
 }
 
-static int __live_parallel_engine1(void *arg)
+struct parallel_thread {
+	struct kthread_worker *worker;
+	struct kthread_work work;
+	struct intel_engine_cs *engine;
+	int result;
+};
+
+static void __live_parallel_engine1(struct kthread_work *work)
 {
-	struct intel_engine_cs *engine = arg;
+	struct parallel_thread *thread =
+		container_of(work, typeof(*thread), work);
+	struct intel_engine_cs *engine = thread->engine;
 	IGT_TIMEOUT(end_time);
 	unsigned long count;
 	int err = 0;
@@ -1452,12 +1481,14 @@ static int __live_parallel_engine1(void *arg)
 	intel_engine_pm_put(engine);
 
 	pr_info("%s: %lu request + sync\n", engine->name, count);
-	return err;
+	thread->result = err;
 }
 
-static int __live_parallel_engineN(void *arg)
+static void __live_parallel_engineN(struct kthread_work *work)
 {
-	struct intel_engine_cs *engine = arg;
+	struct parallel_thread *thread =
+		container_of(work, typeof(*thread), work);
+	struct intel_engine_cs *engine = thread->engine;
 	IGT_TIMEOUT(end_time);
 	unsigned long count;
 	int err = 0;
@@ -1479,7 +1510,7 @@ static int __live_parallel_engineN(void *arg)
 	intel_engine_pm_put(engine);
 
 	pr_info("%s: %lu requests\n", engine->name, count);
-	return err;
+	thread->result = err;
 }
 
 static bool wake_all(struct drm_i915_private *i915)
@@ -1505,9 +1536,11 @@ static int wait_for_all(struct drm_i915_private *i915)
 	return -ETIME;
 }
 
-static int __live_parallel_spin(void *arg)
+static void __live_parallel_spin(struct kthread_work *work)
 {
-	struct intel_engine_cs *engine = arg;
+	struct parallel_thread *thread =
+		container_of(work, typeof(*thread), work);
+	struct intel_engine_cs *engine = thread->engine;
 	struct igt_spinner spin;
 	struct i915_request *rq;
 	int err = 0;
@@ -1520,7 +1553,8 @@ static int __live_parallel_spin(void *arg)
 
 	if (igt_spinner_init(&spin, engine->gt)) {
 		wake_all(engine->i915);
-		return -ENOMEM;
+		thread->result = -ENOMEM;
+		return;
 	}
 
 	intel_engine_pm_get(engine);
@@ -1553,22 +1587,22 @@ static int __live_parallel_spin(void *arg)
 
 out_spin:
 	igt_spinner_fini(&spin);
-	return err;
+	thread->result = err;
 }
 
 static int live_parallel_engines(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
-	static int (* const func[])(void *arg) = {
+	static void (* const func[])(struct kthread_work *) = {
 		__live_parallel_engine1,
 		__live_parallel_engineN,
 		__live_parallel_spin,
 		NULL,
 	};
 	const unsigned int nengines = num_uabi_engines(i915);
+	struct parallel_thread *threads;
 	struct intel_engine_cs *engine;
-	int (* const *fn)(void *arg);
-	struct task_struct **tsk;
+	void (* const *fn)(struct kthread_work *);
 	int err = 0;
 
 	/*
@@ -1576,8 +1610,8 @@ static int live_parallel_engines(void *arg)
 	 * tests that we load up the system maximally.
 	 */
 
-	tsk = kcalloc(nengines, sizeof(*tsk), GFP_KERNEL);
-	if (!tsk)
+	threads = kcalloc(nengines, sizeof(*threads), GFP_KERNEL);
+	if (!threads)
 		return -ENOMEM;
 
 	for (fn = func; !err && *fn; fn++) {
@@ -1594,37 +1628,44 @@ static int live_parallel_engines(void *arg)
 
 		idx = 0;
 		for_each_uabi_engine(engine, i915) {
-			tsk[idx] = kthread_run(*fn, engine,
-					       "igt/parallel:%s",
-					       engine->name);
-			if (IS_ERR(tsk[idx])) {
-				err = PTR_ERR(tsk[idx]);
+			struct kthread_worker *worker;
+
+			worker = kthread_create_worker(0, "igt/parallel:%s",
+						       engine->name);
+			if (IS_ERR(worker)) {
+				err = PTR_ERR(worker);
 				break;
 			}
-			get_task_struct(tsk[idx++]);
-		}
 
-		yield(); /* start all threads before we kthread_stop() */
+			threads[idx].worker = worker;
+			threads[idx].result = 0;
+			threads[idx].engine = engine;
+
+			kthread_init_work(&threads[idx].work, *fn);
+			kthread_queue_work(worker, &threads[idx].work);
+			idx++;
+		}
 
 		idx = 0;
 		for_each_uabi_engine(engine, i915) {
 			int status;
 
-			if (IS_ERR(tsk[idx]))
+			if (!threads[idx].worker)
 				break;
 
-			status = kthread_stop(tsk[idx]);
+			kthread_flush_work(&threads[idx].work);
+			status = READ_ONCE(threads[idx].result);
 			if (status && !err)
 				err = status;
 
-			put_task_struct(tsk[idx++]);
+			kthread_destroy_worker(threads[idx++].worker);
 		}
 
 		if (igt_live_test_end(&t))
 			err = -EIO;
 	}
 
-	kfree(tsk);
+	kfree(threads);
 	return err;
 }
 
@@ -1672,7 +1713,7 @@ static int live_breadcrumbs_smoketest(void *arg)
 	const unsigned int ncpus = num_online_cpus();
 	unsigned long num_waits, num_fences;
 	struct intel_engine_cs *engine;
-	struct task_struct **threads;
+	struct smoke_thread *threads;
 	struct igt_live_test live;
 	intel_wakeref_t wakeref;
 	struct smoketest *smoke;
@@ -1746,23 +1787,26 @@ static int live_breadcrumbs_smoketest(void *arg)
 			 smoke[idx].max_batch, engine->name);
 
 		for (n = 0; n < ncpus; n++) {
-			struct task_struct *tsk;
+			unsigned int i = idx * ncpus + n;
+			struct kthread_worker *worker;
 
-			tsk = kthread_run(__igt_breadcrumbs_smoketest,
-					  &smoke[idx], "igt/%d.%d", idx, n);
-			if (IS_ERR(tsk)) {
-				ret = PTR_ERR(tsk);
+			worker = kthread_create_worker(0, "igt/%d.%d", idx, n);
+			if (IS_ERR(worker)) {
+				ret = PTR_ERR(worker);
 				goto out_flush;
 			}
 
-			get_task_struct(tsk);
-			threads[idx * ncpus + n] = tsk;
+			threads[i].worker = worker;
+			threads[i].t = &smoke[idx];
+
+			kthread_init_work(&threads[i].work,
+					  __igt_breadcrumbs_smoketest);
+			kthread_queue_work(worker, &threads[i].work);
 		}
 
 		idx++;
 	}
 
-	yield(); /* start all threads before we begin */
 	msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
 
 out_flush:
@@ -1771,17 +1815,19 @@ out_flush:
 	num_fences = 0;
 	for_each_uabi_engine(engine, i915) {
 		for (n = 0; n < ncpus; n++) {
-			struct task_struct *tsk = threads[idx * ncpus + n];
+			unsigned int i = idx * ncpus + n;
 			int err;
 
-			if (!tsk)
+			if (!threads[i].worker)
 				continue;
 
-			err = kthread_stop(tsk);
+			WRITE_ONCE(threads[i].stop, true);
+			kthread_flush_work(&threads[i].work);
+			err = READ_ONCE(threads[i].result);
 			if (err < 0 && !ret)
 				ret = err;
 
-			put_task_struct(tsk);
+			kthread_destroy_worker(threads[i].worker);
 		}
 
 		num_waits += atomic_long_read(&smoke[idx].num_waits);
@@ -2891,9 +2937,18 @@ out:
 	return err;
 }
 
-static int p_sync0(void *arg)
+struct p_thread {
+	struct perf_stats p;
+	struct kthread_worker *worker;
+	struct kthread_work work;
+	struct intel_engine_cs *engine;
+	int result;
+};
+
+static void p_sync0(struct kthread_work *work)
 {
-	struct perf_stats *p = arg;
+	struct p_thread *thread = container_of(work, typeof(*thread), work);
+	struct perf_stats *p = &thread->p;
 	struct intel_engine_cs *engine = p->engine;
 	struct intel_context *ce;
 	IGT_TIMEOUT(end_time);
@@ -2902,13 +2957,16 @@ static int p_sync0(void *arg)
 	int err = 0;
 
 	ce = intel_context_create(engine);
-	if (IS_ERR(ce))
-		return PTR_ERR(ce);
+	if (IS_ERR(ce)) {
+		thread->result = PTR_ERR(ce);
+		return;
+	}
 
 	err = intel_context_pin(ce);
 	if (err) {
 		intel_context_put(ce);
-		return err;
+		thread->result = err;
+		return;
 	}
 
 	if (intel_engine_supports_stats(engine)) {
@@ -2958,12 +3016,13 @@ static int p_sync0(void *arg)
 
 	intel_context_unpin(ce);
 	intel_context_put(ce);
-	return err;
+	thread->result = err;
 }
 
-static int p_sync1(void *arg)
+static void p_sync1(struct kthread_work *work)
 {
-	struct perf_stats *p = arg;
+	struct p_thread *thread = container_of(work, typeof(*thread), work);
+	struct perf_stats *p = &thread->p;
 	struct intel_engine_cs *engine = p->engine;
 	struct i915_request *prev = NULL;
 	struct intel_context *ce;
@@ -2973,13 +3032,16 @@ static int p_sync1(void *arg)
 	int err = 0;
 
 	ce = intel_context_create(engine);
-	if (IS_ERR(ce))
-		return PTR_ERR(ce);
+	if (IS_ERR(ce)) {
+		thread->result = PTR_ERR(ce);
+		return;
+	}
 
 	err = intel_context_pin(ce);
 	if (err) {
 		intel_context_put(ce);
-		return err;
+		thread->result = err;
+		return;
 	}
 
 	if (intel_engine_supports_stats(engine)) {
@@ -3031,12 +3093,13 @@ static int p_sync1(void *arg)
 
 	intel_context_unpin(ce);
 	intel_context_put(ce);
-	return err;
+	thread->result = err;
 }
 
-static int p_many(void *arg)
+static void p_many(struct kthread_work *work)
 {
-	struct perf_stats *p = arg;
+	struct p_thread *thread = container_of(work, typeof(*thread), work);
+	struct perf_stats *p = &thread->p;
 	struct intel_engine_cs *engine = p->engine;
 	struct intel_context *ce;
 	IGT_TIMEOUT(end_time);
@@ -3045,13 +3108,16 @@ static int p_many(void *arg)
 	bool busy;
 
 	ce = intel_context_create(engine);
-	if (IS_ERR(ce))
-		return PTR_ERR(ce);
+	if (IS_ERR(ce)) {
+		thread->result = PTR_ERR(ce);
+		return;
+	}
 
 	err = intel_context_pin(ce);
 	if (err) {
 		intel_context_put(ce);
-		return err;
+		thread->result = err;
+		return;
 	}
 
 	if (intel_engine_supports_stats(engine)) {
@@ -3092,26 +3158,23 @@ static int p_many(void *arg)
 
 	intel_context_unpin(ce);
 	intel_context_put(ce);
-	return err;
+	thread->result = err;
 }
 
 static int perf_parallel_engines(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
-	static int (* const func[])(void *arg) = {
+	static void (* const func[])(struct kthread_work *) = {
 		p_sync0,
 		p_sync1,
 		p_many,
 		NULL,
 	};
 	const unsigned int nengines = num_uabi_engines(i915);
+	void (* const *fn)(struct kthread_work *);
 	struct intel_engine_cs *engine;
-	int (* const *fn)(void *arg);
 	struct pm_qos_request qos;
-	struct {
-		struct perf_stats p;
-		struct task_struct *tsk;
-	} *engines;
+	struct p_thread *engines;
 	int err = 0;
 
 	engines = kcalloc(nengines, sizeof(*engines), GFP_KERNEL);
@@ -3134,36 +3197,45 @@ static int perf_parallel_engines(void *arg)
 
 		idx = 0;
 		for_each_uabi_engine(engine, i915) {
+			struct kthread_worker *worker;
+
 			intel_engine_pm_get(engine);
 
 			memset(&engines[idx].p, 0, sizeof(engines[idx].p));
-			engines[idx].p.engine = engine;
 
-			engines[idx].tsk = kthread_run(*fn, &engines[idx].p,
-						       "igt:%s", engine->name);
-			if (IS_ERR(engines[idx].tsk)) {
-				err = PTR_ERR(engines[idx].tsk);
+			worker = kthread_create_worker(0, "igt:%s",
+						       engine->name);
+			if (IS_ERR(worker)) {
+				err = PTR_ERR(worker);
 				intel_engine_pm_put(engine);
 				break;
 			}
-			get_task_struct(engines[idx++].tsk);
-		}
+			engines[idx].worker = worker;
+			engines[idx].result = 0;
+			engines[idx].p.engine = engine;
+			engines[idx].engine = engine;
 
-		yield(); /* start all threads before we kthread_stop() */
+			kthread_init_work(&engines[idx].work, *fn);
+			kthread_queue_work(worker, &engines[idx].work);
+			idx++;
+		}
 
 		idx = 0;
 		for_each_uabi_engine(engine, i915) {
 			int status;
 
-			if (IS_ERR(engines[idx].tsk))
+			if (!engines[idx].worker)
 				break;
 
-			status = kthread_stop(engines[idx].tsk);
+			kthread_flush_work(&engines[idx].work);
+			status = READ_ONCE(engines[idx].result);
 			if (status && !err)
 				err = status;
 
 			intel_engine_pm_put(engine);
-			put_task_struct(engines[idx++].tsk);
+
+			kthread_destroy_worker(engines[idx].worker);
+			idx++;
 		}
 
 		if (igt_live_test_end(&t))