[PATCH libinput v2 2/2] evdev: ratelimit SYN_DROPPED logging

[David Herrmann]

Use the ratelimit helpers for SYN_DROPPED logging. This guarantees that we
will still receive SYN_DROPPED log-messages after multiple days of
runtime, even though there might have been a SYN_DROPPED flood at one
point in time.

Signed-off-by: David Herrmann <dh.herrmann at gmail.com>
---
 src/evdev.c | 18 ++++++++++++------
 src/evdev.h |  4 +---
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/evdev.c b/src/evdev.c
index 3aa87a7..0e2d54d 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -926,15 +926,19 @@ evdev_device_dispatch(void *data)
 		rc = libevdev_next_event(device->evdev,
 					 LIBEVDEV_READ_FLAG_NORMAL, &ev);
 		if (rc == LIBEVDEV_READ_STATUS_SYNC) {
-			if (device->syn_drops_received < 10) {
-				device->syn_drops_received++;
+			switch (ratelimit_test(&device->syn_drop_limit)) {
+			case RATELIMIT_PASS:
 				log_info(libinput, "SYN_DROPPED event from "
 					 "\"%s\" - some input events have "
 					 "been lost.\n", device->devname);
-				if (device->syn_drops_received == 10)
-					log_info(libinput, "No longer logging "
-						 "SYN_DROPPED events for "
-						 "\"%s\"\n", device->devname);
+				break;
+			case RATELIMIT_THRESHOLD:
+				log_info(libinput, "SYN_DROPPED flood "
+					 "from \"%s\"\n",
+					 device->devname);
+				break;
+			case RATELIMIT_EXCEEDED:
+				break;
 			}
 
 			/* send one more sync event so we handle all
@@ -1296,6 +1300,8 @@ evdev_device_create(struct libinput_seat *seat,
 	device->scroll.threshold = 5.0; /* Default may be overridden */
 	device->scroll.direction = 0;
 	device->dpi = DEFAULT_MOUSE_DPI;
+	/* at most 5 SYN_DROPPED log-messages per 30s */
+	ratelimit_init(&device->syn_drop_limit, 30ULL * 1000, 5);
 
 	matrix_init_identity(&device->abs.calibration);
 	matrix_init_identity(&device->abs.usermatrix);
diff --git a/src/evdev.h b/src/evdev.h
index 666c8dc..eefbb79 100644
--- a/src/evdev.h
+++ b/src/evdev.h
@@ -137,9 +137,7 @@ struct evdev_device {
 	} buttons;
 
 	int dpi; /* HW resolution */
-	/* The number of times libevdev processes a SYN_DROPPED, so we can
-	 * stop logging them to avoid flooding the logs. */
-	int syn_drops_received;
+	struct ratelimit syn_drop_limit; /* ratelimit for SYN_DROPPED logging */
 };
 
 #define EVDEV_UNHANDLED_DEVICE ((struct evdev_device *) 1)
-- 
2.1.3