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From:   Sebastian Urban <surban@surban.net>
To:     linux-bluetooth@vger.kernel.org
Cc:     Sebastian Urban <surban@surban.net>
Subject: [PATCH BlueZ] gatt-database: No multiple calls to AcquireWrite
Date:   Sat, 12 Jun 2021 11:56:01 +0200
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This checks if an outstanding call to AcquireWrite is already in
progress. If so, the write request is placed into the queue, but
AcquireWrite is not called again. When a response to AcquireWrite is
received, acquire_write_reply sends all queued writes over the acquired
socket.

Making multiple simultaneous calls to AcquireWrite makes no sense,
as this would open multiple socket pairs and only the last returned
socket would be used for further writes.
---
 src/gatt-database.c | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/src/gatt-database.c b/src/gatt-database.c
index be6dfb265..8cf60c597 100644
--- a/src/gatt-database.c
+++ b/src/gatt-database.c
@@ -2378,6 +2378,26 @@ static struct pending_op *send_write(struct btd_device *device,
 	return NULL;
 }
 
+static void flush_pending_write(void *data, void *user_data)
+{
+	GDBusProxy *proxy = user_data;
+	struct pending_op *op = data;
+
+	if (g_dbus_proxy_method_call(proxy, "WriteValue", write_setup_cb,
+					write_reply_cb,
+					op, pending_op_free) == TRUE)
+		return;
+
+	pending_op_free(op);
+}
+
+static void flush_pending_writes(GDBusProxy *proxy,
+					struct queue *owner_queue)
+{
+	queue_foreach(owner_queue, flush_pending_write, proxy);
+	queue_remove_all(owner_queue, NULL, NULL, NULL);
+}
+
 static bool sock_hup(struct io *io, void *user_data)
 {
 	struct external_chrc *chrc = user_data;
@@ -2488,18 +2508,19 @@ static void acquire_write_reply(DBusMessage *message, void *user_data)
 
 	chrc->write_io = sock_io_new(fd, chrc);
 
-	if (sock_io_send(chrc->write_io, op->data.iov_base,
-				op->data.iov_len) < 0)
-		goto retry;
+	while ((op = queue_peek_head(chrc->pending_writes)) != NULL) {
+		if (sock_io_send(chrc->write_io, op->data.iov_base,
+					op->data.iov_len) < 0)
+			goto retry;
 
-	gatt_db_attribute_write_result(op->attrib, op->id, 0);
+		gatt_db_attribute_write_result(op->attrib, op->id, 0);
+		pending_op_free(op);
+	}
 
 	return;
 
 retry:
-	send_write(op->device, op->attrib, chrc->proxy, NULL, op->id,
-				op->data.iov_base, op->data.iov_len, 0,
-				op->link_type, false, false);
+	flush_pending_writes(chrc->proxy, chrc->pending_writes);
 }
 
 static void acquire_write_setup(DBusMessageIter *iter, void *user_data)
@@ -2527,14 +2548,18 @@ static struct pending_op *acquire_write(struct external_chrc *chrc,
 					uint8_t link_type)
 {
 	struct pending_op *op;
+	bool acquiring = !queue_isempty(chrc->pending_writes);
 
 	op = pending_write_new(device, chrc->pending_writes, attrib, id, value,
 				len, 0, link_type, false, false);
 
+	if (acquiring)
+		return op;
+
 	if (g_dbus_proxy_method_call(chrc->proxy, "AcquireWrite",
 					acquire_write_setup,
 					acquire_write_reply,
-					op, pending_op_free))
+					op, NULL))
 		return op;
 
 	pending_op_free(op);
-- 
2.25.1