MINOR: activity: add accept queue counters for pushed and overflows

It's important to monitor the accept queues to know if some incoming
connections had to be handled by their originating thread due to an
overflow. It's also important to be able to confirm thread fairness.
This patch adds "accq_pushed" to activity reporting, which reports
the number of connections that were successfully pushed into each
thread's queue, and "accq_full", which indicates the number of
connections that couldn't be pushed because the thread's queue was
full.
diff --git a/include/types/activity.h b/include/types/activity.h
index f58d759..9cf4e73 100644
--- a/include/types/activity.h
+++ b/include/types/activity.h
@@ -51,6 +51,8 @@
 	struct freq_ctr cpust_1s;  // avg amount of half-ms stolen over last second
 	struct freq_ctr_period cpust_15s; // avg amount of half-ms stolen over last 15s
 	unsigned int avg_loop_us;  // average run time per loop over last 1024 runs
+	unsigned int accq_pushed;  // accept queue connections pushed
+	unsigned int accq_full;    // accept queue connection not pushed because full
 	char __pad[0]; // unused except to check remaining room
 	char __end[0] __attribute__((aligned(64))); // align size to 64.
 };
diff --git a/src/cli.c b/src/cli.c
index 3c2a55d..ae5e4e8 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1019,6 +1019,8 @@
 	chunk_appendf(&trash, "\ncpust_ms_1s:");  for (thr = 0; thr < global.nbthread; thr++) chunk_appendf(&trash, " %u", read_freq_ctr(&activity[thr].cpust_1s)/2);
 	chunk_appendf(&trash, "\ncpust_ms_15s:"); for (thr = 0; thr < global.nbthread; thr++) chunk_appendf(&trash, " %u", read_freq_ctr_period(&activity[thr].cpust_15s, 15000)/2);
 	chunk_appendf(&trash, "\navg_loop_us:");  for (thr = 0; thr < global.nbthread; thr++) chunk_appendf(&trash, " %u", swrate_avg(activity[thr].avg_loop_us, TIME_STATS_SAMPLES));
+	chunk_appendf(&trash, "\naccq_pushed:");  for (thr = 0; thr < global.nbthread; thr++) chunk_appendf(&trash, " %u", activity[thr].accq_pushed);
+	chunk_appendf(&trash, "\naccq_full:");    for (thr = 0; thr < global.nbthread; thr++) chunk_appendf(&trash, " %u", activity[thr].accq_full);
 
 	chunk_appendf(&trash, "\n");
 
diff --git a/src/listener.c b/src/listener.c
index 2b8c2df..0d7a1c4 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -852,13 +852,14 @@
 			 */
 			ring = &accept_queue_rings[t1];
 			if (accept_queue_push_mp(ring, cfd, l, &addr, laddr)) {
+				HA_ATOMIC_ADD(&activity[t1].accq_pushed, 1);
 				task_wakeup(ring->task, TASK_WOKEN_IO);
 				continue;
 			}
 			/* If the ring is full we do a synchronous accept on
 			 * the local thread here.
-			 * FIXME: we should update some stats here.
 			 */
+			HA_ATOMIC_ADD(&activity[t1].accq_full, 1);
 		}
 #endif // USE_THREAD