write_queue: Enable updating max_length field
Dequeue and free any excess messages, in case the new queue length
is shorter than the old.
Related: OS#5774
Change-Id: Ibfe51a2faf29f8ae160a9c330c9af0d09b5a9002
diff --git a/include/osmocom/core/write_queue.h b/include/osmocom/core/write_queue.h
index 6cb0a6b..fe76282 100644
--- a/include/osmocom/core/write_queue.h
+++ b/include/osmocom/core/write_queue.h
@@ -50,6 +50,7 @@
void osmo_wqueue_clear(struct osmo_wqueue *queue);
int osmo_wqueue_enqueue(struct osmo_wqueue *queue, struct msgb *data);
int osmo_wqueue_enqueue_quiet(struct osmo_wqueue *queue, struct msgb *data);
+size_t osmo_wqueue_set_maxlen(struct osmo_wqueue *queue, unsigned int len);
int osmo_wqueue_bfd_cb(struct osmo_fd *fd, unsigned int what);
/*! @} */
diff --git a/src/core/libosmocore.map b/src/core/libosmocore.map
index c0e164b..30814c3 100644
--- a/src/core/libosmocore.map
+++ b/src/core/libosmocore.map
@@ -565,6 +565,7 @@
osmo_wqueue_clear;
osmo_wqueue_enqueue;
osmo_wqueue_enqueue_quiet;
+osmo_wqueue_set_maxlen;
osmo_wqueue_init;
rate_ctr_add;
rate_ctr_difference;
diff --git a/src/core/write_queue.c b/src/core/write_queue.c
index 884cebd..ffa7704 100644
--- a/src/core/write_queue.c
+++ b/src/core/write_queue.c
@@ -147,4 +147,24 @@
queue->bfd.when &= ~OSMO_FD_WRITE;
}
+/* Update write queue length & drop excess messages.
+ * \param[in] queue linked list header of message queue
+ * \param[in] len new max. wqueue length
+ * \returns Number of messages dropped.
+ *
+ * Messages beyond the new maximum message queue size will be dropped.
+ */
+size_t osmo_wqueue_set_maxlen(struct osmo_wqueue *queue, unsigned int len)
+{
+ size_t dropped_msgs = 0;
+ struct msgb *msg;
+ queue->max_length = len;
+ while (queue->current_length > queue->max_length) {
+ msg = msgb_dequeue_count(&queue->msg_queue, &queue->current_length);
+ msgb_free(msg);
+ dropped_msgs++;
+ }
+ return dropped_msgs;
+}
+
/*! @} */
diff --git a/tests/write_queue/wqueue_test.c b/tests/write_queue/wqueue_test.c
index 3823ef5..d4476f1 100644
--- a/tests/write_queue/wqueue_test.c
+++ b/tests/write_queue/wqueue_test.c
@@ -1,3 +1,14 @@
+/*
+ * (C) 2023 by sysmocom - s.f.m.c. GmbH.
+ * Authors: Holger Hans Peter Freyther
+ * Alexander Rehbein
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
#include <osmocom/core/logging.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/write_queue.h>
@@ -15,6 +26,7 @@
struct msgb *msg;
struct osmo_wqueue wqueue;
int rc;
+ size_t dropped_msgs;
osmo_wqueue_init(&wqueue, 0);
OSMO_ASSERT(wqueue.max_length == 0);
@@ -63,6 +75,46 @@
OSMO_ASSERT(wqueue.current_length == 2);
msgb_free(msg);
osmo_wqueue_clear(&wqueue);
+
+ /* Update limit */
+ OSMO_ASSERT(osmo_wqueue_set_maxlen(&wqueue, 5) == 0);
+ OSMO_ASSERT(osmo_wqueue_set_maxlen(&wqueue, 1) == 0);
+ OSMO_ASSERT(osmo_wqueue_set_maxlen(&wqueue, 4) == 0);
+
+ /* Add three, update limit to 1 */
+ OSMO_ASSERT(wqueue.max_length == 4);
+ msg = msgb_alloc(4096, "msg6");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(rc == 0);
+ OSMO_ASSERT(wqueue.current_length == 1);
+ msg = msgb_alloc(4096, "msg7");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(rc == 0);
+ OSMO_ASSERT(wqueue.current_length == 2);
+ msg = msgb_alloc(4096, "msg8");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(wqueue.current_length == 3);
+ dropped_msgs = osmo_wqueue_set_maxlen(&wqueue, 1);
+ OSMO_ASSERT(dropped_msgs == 2);
+ osmo_wqueue_clear(&wqueue);
+
+ /* Add three, reduce limit to 3 from 6 */
+ OSMO_ASSERT(osmo_wqueue_set_maxlen(&wqueue, 6) == 0);
+ OSMO_ASSERT(wqueue.max_length == 6);
+ msg = msgb_alloc(4096, "msg9");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(rc == 0);
+ OSMO_ASSERT(wqueue.current_length == 1);
+ msg = msgb_alloc(4096, "msg10");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(rc == 0);
+ OSMO_ASSERT(wqueue.current_length == 2);
+ msg = msgb_alloc(4096, "msg11");
+ rc = osmo_wqueue_enqueue(&wqueue, msg);
+ OSMO_ASSERT(wqueue.current_length == 3);
+ dropped_msgs = osmo_wqueue_set_maxlen(&wqueue, 3);
+ OSMO_ASSERT(dropped_msgs == 0);
+ osmo_wqueue_clear(&wqueue);
}
int main(int argc, char **argv)