[PATCH 4/4] dma-buf/fence-chain: Wait on each tested chain link

[Janusz Krzysztofik]

Userspace may build dma_fence chains of arbitrary length step by step,
e.g. via drm_syncobj IOCTLs, and each step may start waiting on a chain
link it has added.

Adjust the wait_* selftests to cover such extreme use cases.

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
---
 drivers/dma-buf/st-dma-fence-chain.c | 118 +++++++++++++++++++++------
 1 file changed, 91 insertions(+), 27 deletions(-)

diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 28763fc797c69..0e7a24ed7caeb 100644
--- a/drivers/dma-buf/st-dma-fence-chain.c
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -568,23 +568,34 @@ static int __wait_fence_chains(void *arg)
 
 static int wait_forward(void *arg)
 {
+	struct task_struct **tsk;
 	struct fence_chains fc;
-	struct task_struct *tsk;
 	ktime_t dt;
+	int i = 0;
 	int err;
-	int i;
 
 	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
 	if (err)
 		return err;
 
-	tsk = kthread_run(__wait_fence_chains, fc.tail, "dmabuf/wait");
-	if (IS_ERR(tsk)) {
-		err = PTR_ERR(tsk);
+	tsk = kmalloc_array(fc.chain_length, sizeof(*tsk), GFP_KERNEL);
+	if (!tsk) {
+		err = -ENOMEM;
 		goto err;
 	}
-	get_task_struct(tsk);
-	yield_to(tsk, true);
+
+	for (i = 0; i < fc.chain_length; i++) {
+		tsk[i] = kthread_run(__wait_fence_chains, fc.chains[i],
+				     "dmabuf/wait-%llu", fc.fences[i]->seqno);
+		if (IS_ERR(tsk[i])) {
+			err = PTR_ERR(tsk[i]);
+			pr_err("Reported %d for kthread_run(%llu)!\n",
+			       err, fc.fences[i]->seqno);
+			goto err;
+		}
+		get_task_struct(tsk[i]);
+		yield_to(tsk[i], true);
+	}
 
 	dt = -ktime_get();
 	for (i = 0; i < fc.chain_length; i++)
@@ -593,32 +604,53 @@ static int wait_forward(void *arg)
 
 	pr_info("%s: %d signals in %llu ns\n", __func__, fc.chain_length, ktime_to_ns(dt));
 
-	err = kthread_stop_put(tsk);
-
 err:
+	while (i--) {
+		int tsk_err = kthread_stop_put(tsk[i]);
+
+		if (tsk_err)
+			pr_err("Reported %d for kthread_stop_put(%llu)!\n",
+			       tsk_err, fc.fences[i]->seqno);
+
+		if (!err)
+			err = tsk_err;
+	}
+	kfree(tsk);
+
 	fence_chains_fini(&fc);
 	return err;
 }
 
 static int wait_backward(void *arg)
 {
+	struct task_struct **tsk;
 	struct fence_chains fc;
-	struct task_struct *tsk;
 	ktime_t dt;
+	int i = 0;
 	int err;
-	int i;
 
 	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
 	if (err)
 		return err;
 
-	tsk = kthread_run(__wait_fence_chains, fc.tail, "dmabuf/wait");
-	if (IS_ERR(tsk)) {
-		err = PTR_ERR(tsk);
+	tsk = kmalloc_array(fc.chain_length, sizeof(*tsk), GFP_KERNEL);
+	if (!tsk) {
+		err = -ENOMEM;
 		goto err;
 	}
-	get_task_struct(tsk);
-	yield_to(tsk, true);
+
+	for (i = 0; i < fc.chain_length; i++) {
+		tsk[i] = kthread_run(__wait_fence_chains, fc.chains[i],
+				     "dmabuf/wait-%llu", fc.fences[i]->seqno);
+		if (IS_ERR(tsk[i])) {
+			err = PTR_ERR(tsk[i]);
+			pr_err("Reported %d for kthread_run(%llu)!\n",
+			       err, fc.fences[i]->seqno);
+			goto err;
+		}
+		get_task_struct(tsk[i]);
+		yield_to(tsk[i], true);
+	}
 
 	dt = -ktime_get();
 	for (i = fc.chain_length; i--; )
@@ -627,9 +659,20 @@ static int wait_backward(void *arg)
 
 	pr_info("%s: %d signals in %llu ns\n", __func__, fc.chain_length, ktime_to_ns(dt));
 
-	err = kthread_stop_put(tsk);
-
+	i = fc.chain_length;
 err:
+	while (i--) {
+		int tsk_err = kthread_stop_put(tsk[i]);
+
+		if (tsk_err)
+			pr_err("Reported %d for kthread_stop_put(%llu)!\n",
+			       tsk_err, fc.fences[i]->seqno);
+
+		if (!err)
+			err = tsk_err;
+	}
+	kfree(tsk);
+
 	fence_chains_fini(&fc);
 	return err;
 }
@@ -652,11 +695,11 @@ static void randomise_fences(struct fence_chains *fc)
 
 static int wait_random(void *arg)
 {
+	struct task_struct **tsk;
 	struct fence_chains fc;
-	struct task_struct *tsk;
 	ktime_t dt;
+	int i = 0;
 	int err;
-	int i;
 
 	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
 	if (err)
@@ -664,13 +707,24 @@ static int wait_random(void *arg)
 
 	randomise_fences(&fc);
 
-	tsk = kthread_run(__wait_fence_chains, fc.tail, "dmabuf/wait");
-	if (IS_ERR(tsk)) {
-		err = PTR_ERR(tsk);
+	tsk = kmalloc_array(fc.chain_length, sizeof(*tsk), GFP_KERNEL);
+	if (!tsk) {
+		err = -ENOMEM;
 		goto err;
 	}
-	get_task_struct(tsk);
-	yield_to(tsk, true);
+
+	for (i = 0; i < fc.chain_length; i++) {
+		tsk[i] = kthread_run(__wait_fence_chains, fc.chains[i],
+				     "dmabuf/wait-%llu", fc.fences[i]->seqno);
+		if (IS_ERR(tsk[i])) {
+			err = PTR_ERR(tsk[i]);
+			pr_err("Reported %d for kthread_run(%llu)!\n",
+			       err, fc.fences[i]->seqno);
+			goto err;
+		}
+		get_task_struct(tsk[i]);
+		yield_to(tsk[i], true);
+	}
 
 	dt = -ktime_get();
 	for (i = 0; i < fc.chain_length; i++)
@@ -679,9 +733,19 @@ static int wait_random(void *arg)
 
 	pr_info("%s: %d signals in %llu ns\n", __func__, fc.chain_length, ktime_to_ns(dt));
 
-	err = kthread_stop_put(tsk);
-
 err:
+	while (i--) {
+		int tsk_err = kthread_stop_put(tsk[i]);
+
+		if (tsk_err)
+			pr_err("Reported %d for kthread_stop_put(%llu)!\n",
+			       tsk_err, fc.fences[i]->seqno);
+
+		if (!err)
+			err = tsk_err;
+	}
+	kfree(tsk);
+
 	fence_chains_fini(&fc);
 	return err;
 }
-- 
2.50.1