[LEDE-DEV] [PATCH] ubusd: Use linked list for queued messages

[Benjamin Hansmann]

The fixed size array for queuing messages led to discarding messages
when it was full, using a linked list instead solves this issue.

Having the list_head link in the ubus_msg_buf itself avoids the
allocation of more memory for an independent list.

The motivation was that for a recursive "ubus list" the function
ubusd_proto.c:ubusd_handle_lookup() produces more than n messages in
one uloop cycle when n objects are registered on the bus.

Signed-off-by: Benjamin Hansmann <i at qbox.audio>
---
 ubusd.c       | 19 ++++++++-----------
 ubusd.h       |  6 +++---
 ubusd_proto.c |  1 +
 3 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/ubusd.c b/ubusd.c
index ba1ff07..b7e1f79 100644
--- a/ubusd.c
+++ b/ubusd.c
@@ -138,11 +138,8 @@ static int ubus_msg_writev(int fd, struct ubus_msg_buf *ub, int offset)
 
 static void ubus_msg_enqueue(struct ubus_client *cl, struct ubus_msg_buf *ub)
 {
-	if (cl->tx_queue[cl->txq_tail])
-		return;
-
-	cl->tx_queue[cl->txq_tail] = ubus_msg_ref(ub);
-	cl->txq_tail = (cl->txq_tail + 1) % ARRAY_SIZE(cl->tx_queue);
+	struct ubus_msg_buf *qub = ubus_msg_ref(ub);
+	list_add_tail(&qub->queue, &cl->tx_queue);
 }
 
 /* takes the msgbuf reference */
@@ -153,7 +150,7 @@ void ubus_msg_send(struct ubus_client *cl, struct ubus_msg_buf *ub)
 	if (ub->hdr.type != UBUS_MSG_MONITOR)
 		ubusd_monitor_message(cl, ub, true);
 
-	if (!cl->tx_queue[cl->txq_cur]) {
+	if (list_empty(&cl->tx_queue)) {
 		written = ubus_msg_writev(cl->sock.fd, ub, 0);
 
 		if (written < 0)
@@ -172,20 +169,20 @@ void ubus_msg_send(struct ubus_client *cl, struct ubus_msg_buf *ub)
 
 static struct ubus_msg_buf *ubus_msg_head(struct ubus_client *cl)
 {
-	return cl->tx_queue[cl->txq_cur];
+	if (list_empty(&cl->tx_queue))
+		return NULL;
+	return list_first_entry(&cl->tx_queue, struct ubus_msg_buf, queue);
 }
 
 static void ubus_msg_dequeue(struct ubus_client *cl)
 {
 	struct ubus_msg_buf *ub = ubus_msg_head(cl);
-
 	if (!ub)
 		return;
 
-	ubus_msg_free(ub);
+	list_del_init(&ub->queue);
 	cl->txq_ofs = 0;
-	cl->tx_queue[cl->txq_cur] = NULL;
-	cl->txq_cur = (cl->txq_cur + 1) % ARRAY_SIZE(cl->tx_queue);
+	ubus_msg_free(ub);
 }
 
 static void handle_client_disconnect(struct ubus_client *cl)
diff --git a/ubusd.h b/ubusd.h
index 4d87920..375f31f 100644
--- a/ubusd.h
+++ b/ubusd.h
@@ -23,13 +23,13 @@
 #include "ubusmsg.h"
 #include "ubusd_acl.h"
 
-#define UBUSD_CLIENT_BACKLOG	32
 #define UBUS_OBJ_HASH_BITS	4
 
 extern struct blob_buf b;
 
 struct ubus_msg_buf {
 	uint32_t refcount; /* ~0: uses external data buffer */
+	struct list_head queue;
 	struct ubus_msghdr hdr;
 	struct blob_attr *data;
 	int fd;
@@ -48,8 +48,8 @@ struct ubus_client {
 
 	struct list_head objects;
 
-	struct ubus_msg_buf *tx_queue[UBUSD_CLIENT_BACKLOG];
-	unsigned int txq_cur, txq_tail, txq_ofs;
+	struct list_head tx_queue;
+	unsigned int txq_ofs;
 
 	struct ubus_msg_buf *pending_msg;
 	struct ubus_msg_buf *retmsg;
diff --git a/ubusd_proto.c b/ubusd_proto.c
index 2d04b5a..ac9d075 100644
--- a/ubusd_proto.c
+++ b/ubusd_proto.c
@@ -495,6 +495,7 @@ struct ubus_client *ubusd_proto_new_client(int fd, uloop_fd_handler cb)
 		goto free;
 
 	INIT_LIST_HEAD(&cl->objects);
+	INIT_LIST_HEAD(&cl->tx_queue);
 	cl->sock.fd = fd;
 	cl->sock.cb = cb;
 	cl->pending_msg_fd = -1;
-- 
2.11.0