Change in simtrace2[master]: usb_buf: Limit the maximum queue length to 3 elements

[laforge]

laforge has submitted this change. ( https://gerrit.osmocom.org/c/simtrace2/+/16575 )

Change subject: usb_buf: Limit the maximum queue length to 3 elements
......................................................................

usb_buf: Limit the maximum queue length to 3 elements

If there are already three elements in the to-be-transmitted queue
for the EP, let's free the first element of the queue.  This is a
clear indication that the USB host is not polling the endpoint
regularly.  Maybe there's no host application running at all?

This should obsolete Change-Id Ie9ebdd2ff966f67c9afd1ed760f106558f0091ad

Change-Id: Ie15183f16b22193ffdaf01845db2eae4c7f43c17
Closes: OS#4251
---
M firmware/libcommon/source/usb_buf.c
1 file changed, 12 insertions(+), 0 deletions(-)

Approvals:
  Jenkins Builder: Verified
  laforge: Looks good to me, approved



diff --git a/firmware/libcommon/source/usb_buf.c b/firmware/libcommon/source/usb_buf.c
index 8ad5a0e..7892d6e 100644
--- a/firmware/libcommon/source/usb_buf.c
+++ b/firmware/libcommon/source/usb_buf.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 
 #define USB_ALLOC_SIZE	280
+#define USB_MAX_QLEN	3
 
 static struct usb_buffered_ep usb_buffered_ep[BOARD_USB_NUMENDPOINTS];
 
@@ -78,6 +79,17 @@
 
 	/* no need for irqsafe operation, as the usb_tx_queue is
 	 * processed only by the main loop context */
+
+	if (ep->queue_len > USB_MAX_QLEN) {
+		struct msgb *evict;
+		/* free the first pending buffer in the queue */
+		TRACE_INFO("EP%02x: dropping first queue element (qlen=%u)\r\n",
+			   ep->ep, ep->queue_len);
+		evict = msgb_dequeue_count(&ep->queue, &ep->queue_len);
+		OSMO_ASSERT(evict);
+		usb_buf_free(evict);
+	}
+
 	msgb_enqueue_count(&ep->queue, msg, &ep->queue_len);
 	return 0;
 }

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Gerrit-Project: simtrace2
Gerrit-Branch: master
Gerrit-Change-Id: Ie15183f16b22193ffdaf01845db2eae4c7f43c17
Gerrit-Change-Number: 16575
Gerrit-PatchSet: 3
Gerrit-Owner: laforge <laforge at osmocom.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-MessageType: merged
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