diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -1755,7 +1755,7 @@
 	int isipv6;
 #endif /* INET6 */
 	int optlen, tlen, win, ulen;
-	bool incl_opts;
+	bool incl_opts, lock_upgraded;
 	uint16_t port;
 	int output_ret;
 
@@ -2088,21 +2088,29 @@
 	TCP_PROBE3(debug__output, tp, th, m);
 	if (flags & TH_RST)
 		TCP_PROBE5(accept__refused, NULL, NULL, m, tp, nth);
+	lock_upgraded = false;
+	lgb = NULL;
 	if ((tp != NULL) && (tp->t_logstate != TCP_LOG_STATE_OFF)) {
 		union tcp_log_stackspecific log;
 		struct timeval tv;
 
-		memset(&log.u_bbr, 0, sizeof(log.u_bbr));
-		log.u_bbr.inhpts = tp->t_inpcb->inp_in_hpts;
-		log.u_bbr.ininput = tp->t_inpcb->inp_in_input;
-		log.u_bbr.flex8 = 4;
-		log.u_bbr.pkts_out = tp->t_maxseg;
-		log.u_bbr.timeStamp = tcp_get_usecs(&tv);
-		log.u_bbr.delivered = 0;
-		lgb = tcp_log_event_(tp, nth, NULL, NULL, TCP_LOG_OUT, ERRNO_UNK,
-				     0, &log, false, NULL, NULL, 0, &tv);
-	} else
-		lgb = NULL;
+		lock_upgraded = !INP_WLOCKED(inp) && INP_TRY_UPGRADE(inp);
+		/*
+		 *`If we don't already own the write lock and can't upgrade,
+		 * just don't log the event, but still send the response.
+		 */
+		if (INP_WLOCKED(inp)) {
+			memset(&log.u_bbr, 0, sizeof(log.u_bbr));
+			log.u_bbr.inhpts = tp->t_inpcb->inp_in_hpts;
+			log.u_bbr.ininput = tp->t_inpcb->inp_in_input;
+			log.u_bbr.flex8 = 4;
+			log.u_bbr.pkts_out = tp->t_maxseg;
+			log.u_bbr.timeStamp = tcp_get_usecs(&tv);
+			log.u_bbr.delivered = 0;
+			lgb = tcp_log_event_(tp, nth, NULL, NULL, TCP_LOG_OUT, ERRNO_UNK,
+			                     0, &log, false, NULL, NULL, 0, &tv);
+		}
+	}
 
 #ifdef INET6
 	if (isipv6) {
@@ -2119,10 +2127,10 @@
 		output_ret = ip_output(m, NULL, NULL, 0, NULL, inp);
 	}
 #endif
-	if (lgb) {
+	if (lgb != NULL)
 		lgb->tlb_errno = output_ret;
-		lgb = NULL;
-	}
+	if (lock_upgraded)
+		INP_DOWNGRADE(inp);
 }
 
 /*