[PATCH 2/2] staging: greybus: loopback: convert loopback to use generic async operations

[Bryan O'Donoghue]

Loopback has its own internal method for tracking and timing out
asynchronous operations however previous patches make it possible to use
functionality provided by operation.c to do this instead. Using the code in
operation.c means we can completely subtract the timer, the work-queue, the
kref and the cringe-worthy 'pending' flag. The completion callback
triggered by operation.c will provide an authoritative result code -
including -ETIMEDOUT for asynchronous operations.

Signed-off-by: Bryan O'Donoghue <pure.logic@xxxxxxxxxxxxxxxxx>
Cc: Johan Hovold <johan@xxxxxxxxxx>
Cc: Alex Elder <elder@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: greybus-dev@xxxxxxxxxxxxxxxx
Cc: devel@xxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 drivers/staging/greybus/loopback.c | 165 +++++++------------------------------
 1 file changed, 31 insertions(+), 134 deletions(-)

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c
index 3d92638..48599ed 100644
--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -59,11 +59,6 @@ struct gb_loopback_async_operation {
 	struct gb_loopback *gb;
 	struct gb_operation *operation;
 	ktime_t ts;
-	struct timer_list timer;
-	struct list_head entry;
-	struct work_struct work;
-	struct kref kref;
-	bool pending;
 	int (*completion)(struct gb_loopback_async_operation *op_async);
 };
 
@@ -427,56 +422,6 @@ static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
 	return ret;
 }
 
-static void __gb_loopback_async_operation_destroy(struct kref *kref)
-{
-	struct gb_loopback_async_operation *op_async;
-
-	op_async = container_of(kref, struct gb_loopback_async_operation, kref);
-
-	list_del(&op_async->entry);
-	if (op_async->operation)
-		gb_operation_put(op_async->operation);
-	atomic_dec(&op_async->gb->outstanding_operations);
-	wake_up(&op_async->gb->wq_completion);
-	kfree(op_async);
-}
-
-static void gb_loopback_async_operation_get(struct gb_loopback_async_operation
-					    *op_async)
-{
-	kref_get(&op_async->kref);
-}
-
-static void gb_loopback_async_operation_put(struct gb_loopback_async_operation
-					    *op_async)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&gb_dev.lock, flags);
-	kref_put(&op_async->kref, __gb_loopback_async_operation_destroy);
-	spin_unlock_irqrestore(&gb_dev.lock, flags);
-}
-
-static struct gb_loopback_async_operation *
-	gb_loopback_operation_find(u16 id)
-{
-	struct gb_loopback_async_operation *op_async;
-	bool found = false;
-	unsigned long flags;
-
-	spin_lock_irqsave(&gb_dev.lock, flags);
-	list_for_each_entry(op_async, &gb_dev.list_op_async, entry) {
-		if (op_async->operation->id == id) {
-			gb_loopback_async_operation_get(op_async);
-			found = true;
-			break;
-		}
-	}
-	spin_unlock_irqrestore(&gb_dev.lock, flags);
-
-	return found ? op_async : NULL;
-}
-
 static void gb_loopback_async_wait_all(struct gb_loopback *gb)
 {
 	wait_event(gb->wq_completion,
@@ -488,83 +433,41 @@ static void gb_loopback_async_operation_callback(struct gb_operation *operation)
 	struct gb_loopback_async_operation *op_async;
 	struct gb_loopback *gb;
 	ktime_t te;
-	bool err = false;
+	int result;
 
 	te = ktime_get();
-	op_async = gb_loopback_operation_find(operation->id);
-	if (!op_async)
-		return;
-
+	result = gb_operation_result(operation);
+	op_async = gb_operation_get_data(operation);
 	gb = op_async->gb;
+
 	mutex_lock(&gb->mutex);
 
-	if (!op_async->pending || gb_operation_result(operation)) {
-		err = true;
-	} else {
-		if (op_async->completion)
-			if (op_async->completion(op_async))
-				err = true;
-	}
+	if (!result && op_async->completion)
+		result = op_async->completion(op_async);
 
-	if (!err)
+	if (!result) {
 		gb->elapsed_nsecs = gb_loopback_calc_latency(op_async->ts, te);
-
-	if (op_async->pending) {
-		if (err)
-			gb->error++;
-		gb->iteration_count++;
-		op_async->pending = false;
-		del_timer_sync(&op_async->timer);
-		gb_loopback_async_operation_put(op_async);
-		gb_loopback_calculate_stats(gb, err);
+	} else {
+		gb->error++;
+		if (result == -ETIMEDOUT)
+			gb->requests_timedout++;
 	}
-	mutex_unlock(&gb->mutex);
-
-	dev_dbg(&gb->connection->bundle->dev, "complete operation %d\n",
-		operation->id);
-
-	gb_loopback_async_operation_put(op_async);
-}
-
-static void gb_loopback_async_operation_work(struct work_struct *work)
-{
-	struct gb_loopback *gb;
-	struct gb_operation *operation;
-	struct gb_loopback_async_operation *op_async;
 
-	op_async = container_of(work, struct gb_loopback_async_operation, work);
-	gb = op_async->gb;
-	operation = op_async->operation;
+	gb->iteration_count++;
+	gb_loopback_calculate_stats(gb, result);
 
-	mutex_lock(&gb->mutex);
-	if (op_async->pending) {
-		gb->requests_timedout++;
-		gb->error++;
-		gb->iteration_count++;
-		op_async->pending = false;
-		gb_loopback_async_operation_put(op_async);
-		gb_loopback_calculate_stats(gb, true);
-	}
 	mutex_unlock(&gb->mutex);
 
-	dev_dbg(&gb->connection->bundle->dev, "timeout operation %d\n",
+	dev_dbg(&gb->connection->bundle->dev, "complete operation %d\n",
 		operation->id);
 
-	gb_operation_cancel(operation, -ETIMEDOUT);
-	gb_loopback_async_operation_put(op_async);
-}
-
-static void gb_loopback_async_operation_timeout(unsigned long data)
-{
-	struct gb_loopback_async_operation *op_async;
-	u16 id = data;
+	/* Wake up waiters */
+	atomic_dec(&op_async->gb->outstanding_operations);
+	wake_up(&gb->wq_completion);
 
-	op_async = gb_loopback_operation_find(id);
-	if (!op_async) {
-		pr_err("operation %d not found - time out ?\n", id);
-		return;
-	}
-	schedule_work(&op_async->work);
+	/* Release resources */
+	gb_operation_put(operation);
+	kfree(op_async);
 }
 
 static int gb_loopback_async_operation(struct gb_loopback *gb, int type,
@@ -575,15 +478,11 @@ static int gb_loopback_async_operation(struct gb_loopback *gb, int type,
 	struct gb_loopback_async_operation *op_async;
 	struct gb_operation *operation;
 	int ret;
-	unsigned long flags;
 
 	op_async = kzalloc(sizeof(*op_async), GFP_KERNEL);
 	if (!op_async)
 		return -ENOMEM;
 
-	INIT_WORK(&op_async->work, gb_loopback_async_operation_work);
-	kref_init(&op_async->kref);
-
 	operation = gb_operation_create(gb->connection, type, request_size,
 					response_size, GFP_KERNEL);
 	if (!operation) {
@@ -594,33 +493,29 @@ static int gb_loopback_async_operation(struct gb_loopback *gb, int type,
 	if (request_size)
 		memcpy(operation->request->payload, request, request_size);
 
+	gb_operation_set_data(operation, op_async);
+
 	op_async->gb = gb;
 	op_async->operation = operation;
 	op_async->completion = completion;
 
-	spin_lock_irqsave(&gb_dev.lock, flags);
-	list_add_tail(&op_async->entry, &gb_dev.list_op_async);
-	spin_unlock_irqrestore(&gb_dev.lock, flags);
-
 	op_async->ts = ktime_get();
-	op_async->pending = true;
+
 	atomic_inc(&gb->outstanding_operations);
+
 	mutex_lock(&gb->mutex);
 	ret = gb_operation_request_send(operation,
 					gb_loopback_async_operation_callback,
-					0,
+					jiffies_to_msecs(gb->jiffy_timeout),
 					GFP_KERNEL);
 	if (ret)
 		goto error;
 
-	setup_timer(&op_async->timer, gb_loopback_async_operation_timeout,
-			(unsigned long)operation->id);
-	op_async->timer.expires = jiffies + gb->jiffy_timeout;
-	add_timer(&op_async->timer);
-
 	goto done;
 error:
-	gb_loopback_async_operation_put(op_async);
+	atomic_dec(&gb->outstanding_operations);
+	gb_operation_put(operation);
+	kfree(op_async);
 done:
 	mutex_unlock(&gb->mutex);
 	return ret;
@@ -1024,8 +919,10 @@ static int gb_loopback_fn(void *data)
 			else if (type == GB_LOOPBACK_TYPE_SINK)
 				error = gb_loopback_async_sink(gb, size);
 
-			if (error)
+			if (error) {
 				gb->error++;
+				gb->iteration_count++;
+			}
 		} else {
 			/* We are effectively single threaded here */
 			if (type == GB_LOOPBACK_TYPE_PING)
-- 
2.7.4