git: 51cc31088bf4 - main - netmap: bridge: fix transmission in busy-wait mode

[Vincenzo Maffione]

The branch main has been updated by vmaffione:

URL: https://cgit.FreeBSD.org/src/commit/?id=51cc31088bf4d23a6ad0bfe8851adaa049d750fc

commit 51cc31088bf4d23a6ad0bfe8851adaa049d750fc
Author:     Vincenzo Maffione <vmaffione at FreeBSD.org>
AuthorDate: 2021-03-30 06:24:56 +0000
Commit:     Vincenzo Maffione <vmaffione at FreeBSD.org>
CommitDate: 2021-03-30 06:24:56 +0000

    netmap: bridge: fix transmission in busy-wait mode
    
    In busy-wait mode (BUSYWAIT defined), NIOCTXSYNC should be
    performed after packets have been moved to the TX ring
    (rather than before).
    Before the change, moved packets may stall for an indefinite
    time in the TX ring.
    
    MFC after:      1 week
---
 tools/tools/netmap/bridge.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/tools/tools/netmap/bridge.c b/tools/tools/netmap/bridge.c
index 77d235bf6e08..0c8f56265ff4 100644
--- a/tools/tools/netmap/bridge.c
+++ b/tools/tools/netmap/bridge.c
@@ -17,6 +17,10 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+#if defined(_WIN32)
+#define BUSYWAIT
+#endif
+
 static int verbose = 0;
 
 static int do_abort = 0;
@@ -321,21 +325,19 @@ main(int argc, char **argv)
 		pollfd[0].revents = pollfd[1].revents = 0;
 		n0 = rx_slots_avail(pa);
 		n1 = rx_slots_avail(pb);
-#if defined(_WIN32) || defined(BUSYWAIT)
+#ifdef BUSYWAIT
 		if (n0) {
-			ioctl(pollfd[1].fd, NIOCTXSYNC, NULL);
 			pollfd[1].revents = POLLOUT;
 		} else {
 			ioctl(pollfd[0].fd, NIOCRXSYNC, NULL);
 		}
 		if (n1) {
-			ioctl(pollfd[0].fd, NIOCTXSYNC, NULL);
 			pollfd[0].revents = POLLOUT;
 		} else {
 			ioctl(pollfd[1].fd, NIOCRXSYNC, NULL);
 		}
 		ret = 1;
-#else
+#else  /* !defined(BUSYWAIT) */
 		if (n0)
 			pollfd[1].events |= POLLOUT;
 		else
@@ -347,7 +349,7 @@ main(int argc, char **argv)
 
 		/* poll() also cause kernel to txsync/rxsync the NICs */
 		ret = poll(pollfd, 2, 2500);
-#endif /* defined(_WIN32) || defined(BUSYWAIT) */
+#endif /* !defined(BUSYWAIT) */
 		if (ret <= 0 || verbose)
 		    D("poll %s [0] ev %x %x rx %d@%d tx %d,"
 			     " [1] ev %x %x rx %d@%d tx %d",
@@ -375,11 +377,19 @@ main(int argc, char **argv)
 			D("error on fd1, rx [%d,%d,%d)",
 			    rx->head, rx->cur, rx->tail);
 		}
-		if (pollfd[0].revents & POLLOUT)
+		if (pollfd[0].revents & POLLOUT) {
 			ports_move(pb, pa, burst, msg_b2a);
+#ifdef BUSYWAIT
+			ioctl(pollfd[0].fd, NIOCTXSYNC, NULL);
+#endif
+		}
 
-		if (pollfd[1].revents & POLLOUT)
+		if (pollfd[1].revents & POLLOUT) {
 			ports_move(pa, pb, burst, msg_a2b);
+#ifdef BUSYWAIT
+			ioctl(pollfd[1].fd, NIOCTXSYNC, NULL);
+#endif
+		}
 
 		/*
 		 * We don't need ioctl(NIOCTXSYNC) on the two file descriptors.