dma-buf: Add selftests for dma-fence

Exercise the dma-fence API exported to drivers.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190819095928.32091-2-chris@chris-wilson.co.uk

drivers/dma-buf/Makefile

@@ -5,5 +5,8 @@ obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
 obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o
 obj-$(CONFIG_UDMABUF)		+= udmabuf.o
 
-dmabuf_selftests-y := selftest.o
+dmabuf_selftests-y := \
+	selftest.o \
+	st-dma-fence.o
+
 obj-$(CONFIG_DMABUF_SELFTESTS)	+= dmabuf_selftests.o

drivers/dma-buf/selftests.h

@@ -10,3 +10,4 @@
  * Tests are executed in order by igt/dmabuf_selftest
  */
 selftest(sanitycheck, __sanitycheck__) /* keep first (igt selfcheck) */
+selftest(dma_fence, dma_fence)

drivers/dma-buf/st-dma-fence.c

+/* SPDX-License-Identifier: MIT */
+
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-fence.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "selftest.h"
+
+static struct kmem_cache *slab_fences;
+
+static struct mock_fence {
+	struct dma_fence base;
+	struct spinlock lock;
+} *to_mock_fence(struct dma_fence *f) {
+	return container_of(f, struct mock_fence, base);
+}
+
+static const char *mock_name(struct dma_fence *f)
+{
+	return "mock";
+}
+
+static void mock_fence_release(struct dma_fence *f)
+{
+	kmem_cache_free(slab_fences, to_mock_fence(f));
+}
+
+struct wait_cb {
+	struct dma_fence_cb cb;
+	struct task_struct *task;
+};
+
+static void mock_wakeup(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	wake_up_process(container_of(cb, struct wait_cb, cb)->task);
+}
+
+static long mock_wait(struct dma_fence *f, bool intr, long timeout)
+{
+	const int state = intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
+	struct wait_cb cb = { .task = current };
+
+	if (dma_fence_add_callback(f, &cb.cb, mock_wakeup))
+		return timeout;
+
+	while (timeout) {
+		set_current_state(state);
+
+		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &f->flags))
+			break;
+
+		if (signal_pending_state(state, current))
+			break;
+
+		timeout = schedule_timeout(timeout);
+	}
+	__set_current_state(TASK_RUNNING);
+
+	if (!dma_fence_remove_callback(f, &cb.cb))
+		return timeout;
+
+	if (signal_pending_state(state, current))
+		return -ERESTARTSYS;
+
+	return -ETIME;
+}
+
+static const struct dma_fence_ops mock_ops = {
+	.get_driver_name = mock_name,
+	.get_timeline_name = mock_name,
+	.wait = mock_wait,
+	.release = mock_fence_release,
+};
+
+static struct dma_fence *mock_fence(void)
+{
+	struct mock_fence *f;
+
+	f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
+	if (!f)
+		return NULL;
+
+	spin_lock_init(&f->lock);
+	dma_fence_init(&f->base, &mock_ops, &f->lock, 0, 0);
+
+	return &f->base;
+}
+
+static int sanitycheck(void *arg)
+{
+	struct dma_fence *f;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_signal(f);
+	dma_fence_put(f);
+
+	return 0;
+}
+
+static int test_signaling(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_is_signaled(f)) {
+		pr_err("Fence unexpectedly signaled on creation\n");
+		goto err_free;
+	}
+
+	if (dma_fence_signal(f)) {
+		pr_err("Fence reported being already signaled\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_is_signaled(f)) {
+		pr_err("Fence not reporting signaled\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_signal(f)) {
+		pr_err("Fence reported not being already signaled\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+struct simple_cb {
+	struct dma_fence_cb cb;
+	bool seen;
+};
+
+static void simple_callback(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	smp_store_mb(container_of(cb, struct simple_cb, cb)->seen, true);
+}
+
+static int test_add_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!cb.seen) {
+		pr_err("Callback failed!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_late_add_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_signal(f);
+
+	if (!dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Added callback, but fence was already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (cb.seen) {
+		pr_err("Callback called after failed attachment !\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_rm_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_remove_callback(f, &cb.cb)) {
+		pr_err("Failed to remove callback!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (cb.seen) {
+		pr_err("Callback still signaled after removal!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_late_rm_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!cb.seen) {
+		pr_err("Callback failed!\n");
+		goto err_free;
+	}
+
+	if (dma_fence_remove_callback(f, &cb.cb)) {
+		pr_err("Callback removal succeed after being executed!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_status(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_get_status(f)) {
+		pr_err("Fence unexpectedly has signaled status on creation\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!dma_fence_get_status(f)) {
+		pr_err("Fence not reporting signaled status\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_error(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_set_error(f, -EIO);
+
+	if (dma_fence_get_status(f)) {
+		pr_err("Fence unexpectedly has error status before signal\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (dma_fence_get_status(f) != -EIO) {
+		pr_err("Fence not reporting error status, got %d\n",
+		       dma_fence_get_status(f));
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_wait(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_wait_timeout(f, false, 0) != -ETIME) {
+		pr_err("Wait reported complete before being signaled\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+
+	if (dma_fence_wait_timeout(f, false, 0) != 0) {
+		pr_err("Wait reported incomplete after being signaled\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_signal(f);
+	dma_fence_put(f);
+	return err;
+}
+
+struct wait_timer {
+	struct timer_list timer;
+	struct dma_fence *f;
+};
+
+static void wait_timer(struct timer_list *timer)
+{
+	struct wait_timer *wt = from_timer(wt, timer, timer);
+
+	dma_fence_signal(wt->f);
+}
+
+static int test_wait_timeout(void *arg)
+{
+	struct wait_timer wt;
+	int err = -EINVAL;
+
+	timer_setup(&wt.timer, wait_timer, 0);
+
+	wt.f = mock_fence();
+	if (!wt.f)
+		return -ENOMEM;
+
+	if (dma_fence_wait_timeout(wt.f, false, 1) != -ETIME) {
+		pr_err("Wait reported complete before being signaled\n");
+		goto err_free;
+	}
+
+	mod_timer(&wt.timer, jiffies + 1);
+
+	if (dma_fence_wait_timeout(wt.f, false, 2) == -ETIME) {
+		if (timer_pending(&wt.timer)) {
+			pr_notice("Timer did not fire within the jiffie!\n");
+			err = 0; /* not our fault! */
+		} else {
+			pr_err("Wait reported incomplete after timeout\n");
+		}
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	del_timer_sync(&wt.timer);
+	dma_fence_signal(wt.f);
+	dma_fence_put(wt.f);
+	return err;
+}
+
+static int test_stub(void *arg)
+{
+	struct dma_fence *f[64];
+	int err = -EINVAL;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		f[i] = dma_fence_get_stub();
+		if (!dma_fence_is_signaled(f[i])) {
+			pr_err("Obtained unsignaled stub fence!\n");
+			goto err;
+		}
+	}
+
+	err = 0;
+err:
+	while (i--)
+		dma_fence_put(f[i]);
+	return err;
+}
+
+/* Now off to the races! */
+
+struct race_thread {
+	struct dma_fence __rcu **fences;
+	struct task_struct *task;
+	bool before;
+	int id;
+};
+
+static void __wait_for_callbacks(struct dma_fence *f)
+{
+	spin_lock_irq(f->lock);
+	spin_unlock_irq(f->lock);
+}
+
+static int thread_signal_callback(void *arg)
+{
+	const struct race_thread *t = arg;
+	unsigned long pass = 0;
+	unsigned long miss = 0;
+	int err = 0;
+
+	while (!err && !kthread_should_stop()) {
+		struct dma_fence *f1, *f2;
+		struct simple_cb cb;
+
+		f1 = mock_fence();
+		if (!f1) {
+			err = -ENOMEM;
+			break;
+		}
+
+		rcu_assign_pointer(t->fences[t->id], f1);
+		smp_wmb();
+
+		rcu_read_lock();
+		do {
+			f2 = dma_fence_get_rcu_safe(&t->fences[!t->id]);
+		} while (!f2 && !kthread_should_stop());
+		rcu_read_unlock();
+
+		if (t->before)
+			dma_fence_signal(f1);
+
+		smp_store_mb(cb.seen, false);
+		if (!f2 || dma_fence_add_callback(f2, &cb.cb, simple_callback))
+			miss++, cb.seen = true;
+
+		if (!t->before)
+			dma_fence_signal(f1);
+
+		if (!cb.seen) {
+			dma_fence_wait(f2, false);
+			__wait_for_callbacks(f2);
+		}
+
+		if (!READ_ONCE(cb.seen)) {
+			pr_err("Callback not seen on thread %d, pass %lu (%lu misses), signaling %s add_callback; fence signaled? %s\n",
+			       t->id, pass, miss,
+			       t->before ? "before" : "after",
+			       dma_fence_is_signaled(f2) ? "yes" : "no");
+			err = -EINVAL;
+		}
+
+		dma_fence_put(f2);
+
+		rcu_assign_pointer(t->fences[t->id], NULL);
+		smp_wmb();
+
+		dma_fence_put(f1);
+
+		pass++;
+	}
+
+	pr_info("%s[%d] completed %lu passes, %lu misses\n",
+		__func__, t->id, pass, miss);
+	return err;
+}
+
+static int race_signal_callback(void *arg)
+{
+	struct dma_fence __rcu *f[2] = {};
+	int ret = 0;
+	int pass;
+
+	for (pass = 0; !ret && pass <= 1; pass++) {
+		struct race_thread t[2];
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(t); i++) {
+			t[i].fences = f;
+			t[i].id = i;
+			t[i].before = pass;
+			t[i].task = kthread_run(thread_signal_callback, &t[i],
+						"dma-fence:%d", i);
+			get_task_struct(t[i].task);
+		}
+
+		msleep(50);
+
+		for (i = 0; i < ARRAY_SIZE(t); i++) {
+			int err;
+
+			err = kthread_stop(t[i].task);
+			if (err && !ret)
+				ret = err;
+
+			put_task_struct(t[i].task);
+		}
+	}
+
+	return ret;
+}
+
+int dma_fence(void)
+{
+	static const struct subtest tests[] = {
+		SUBTEST(sanitycheck),
+		SUBTEST(test_signaling),
+		SUBTEST(test_add_callback),
+		SUBTEST(test_late_add_callback),
+		SUBTEST(test_rm_callback),
+		SUBTEST(test_late_rm_callback),
+		SUBTEST(test_status),
+		SUBTEST(test_error),
+		SUBTEST(test_wait),
+		SUBTEST(test_wait_timeout),
+		SUBTEST(test_stub),
+		SUBTEST(race_signal_callback),
+	};
+	int ret;
+
+	pr_info("sizeof(dma_fence)=%lu\n", sizeof(struct dma_fence));
+
+	slab_fences = KMEM_CACHE(mock_fence,
+				 SLAB_TYPESAFE_BY_RCU |
+				 SLAB_HWCACHE_ALIGN);
+	if (!slab_fences)
+		return -ENOMEM;
+
+	ret = subtests(tests, NULL);
+
+	kmem_cache_destroy(slab_fences);
+
+	return ret;
+}