diff --git a/sys/sys/sockbuf.h b/sys/sys/sockbuf.h
--- a/sys/sys/sockbuf.h
+++ b/sys/sys/sockbuf.h
@@ -79,9 +79,8 @@
  * Locking key to struct sockbuf:
  * (a) locked by SOCKBUF_LOCK().
  */
-struct	sockbuf {
-	struct	mtx sb_mtx;		/* sockbuf lock */
-	struct	sx sb_sx;		/* prevent I/O interlacing */
+struct sockbuf {
+	struct	mtx *sb_mtx;		/* sockbuf lock */
 	struct	selinfo *sb_sel;	/* process selecting read/write */
 	short	sb_state;	/* (a) socket state on sockbuf */
 #define	sb_startzero	sb_flags
@@ -122,7 +121,7 @@
  * Per-socket buffer mutex used to protect most fields in the socket
  * buffer.
  */
-#define	SOCKBUF_MTX(_sb)		(&(_sb)->sb_mtx)
+#define	SOCKBUF_MTX(_sb)		((_sb)->sb_mtx)
 #define	SOCKBUF_LOCK_INIT(_sb, _name) \
 	mtx_init(SOCKBUF_MTX(_sb), _name, NULL, MTX_DEF)
 #define	SOCKBUF_LOCK_DESTROY(_sb)	mtx_destroy(SOCKBUF_MTX(_sb))
diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
--- a/sys/sys/socketvar.h
+++ b/sys/sys/socketvar.h
@@ -121,6 +121,17 @@
 
 	int so_ts_clock;	/* type of the clock used for timestamps */
 	uint32_t so_max_pacing_rate;	/* (f) TX rate limit in bytes/s */
+
+	/*
+	 * Mutexes to prevent interleaving of socket I/O.  These have to be
+	 * outside of the socket buffers in order to interlock with listen(2).
+	 */
+	struct sx so_snd_sx __aligned(CACHE_LINE_SIZE);
+	struct mtx so_snd_mtx;
+
+	struct sx so_rcv_sx __aligned(CACHE_LINE_SIZE);
+	struct mtx so_rcv_mtx;
+
 	union {
 		/* Regular (data flow) socket. */
 		struct {
@@ -256,13 +267,13 @@
 #define	SBL_VALID	(SBL_WAIT | SBL_NOINTR)
 
 #define	SOCK_IO_SEND_LOCK(so, flags)					\
-	soiolock((so), &(so)->so_snd.sb_sx, (flags))
+	soiolock((so), &(so)->so_snd_sx, (flags))
 #define	SOCK_IO_SEND_UNLOCK(so)						\
-	soiounlock(&(so)->so_snd.sb_sx)
+	soiounlock(&(so)->so_snd_sx)
 #define	SOCK_IO_RECV_LOCK(so, flags)					\
-	soiolock((so), &(so)->so_rcv.sb_sx, (flags))
+	soiolock((so), &(so)->so_rcv_sx, (flags))
 #define	SOCK_IO_RECV_UNLOCK(so)						\
-	soiounlock(&(so)->so_rcv.sb_sx)
+	soiounlock(&(so)->so_rcv_sx)
 
 /*
  * Do we need to notify the other side when I/O is possible?