Index: sys/kern/kern_umtx.c
===================================================================
--- sys/kern/kern_umtx.c
+++ sys/kern/kern_umtx.c
@@ -219,7 +219,7 @@
 	struct timespec end;
 };
 
-#if defined(COMPAT_FREEBSD32)
+#if defined(COMPAT_FREEBSD32) || defined(__LP64__)
 #define	NEED_UMTX32
 #endif
 
@@ -4142,6 +4142,36 @@
 }
 
 #ifdef NEED_UMTX32
+#if defined(__amd64__)
+struct timespecx32 {
+	int64_t			tv_sec;
+	int32_t			tv_nsec;
+};
+
+struct umtx_timex32 {
+	struct	timespecx32	timeout;
+	uint32_t		flags;
+	uint32_t		clockid;
+};
+
+#define	timespeci386	timespec32
+#define	umtx_timei386	umtx_time32
+#else
+struct timespeci386 {
+	int32_t			tv_sec;
+	int32_t			tv_nsec;
+};
+
+struct umtx_timei386 {
+	struct	timespeci386	timeout;
+	uint32_t		flags;
+	uint32_t		clockid;
+};
+
+#define	timespecx32	timespec32
+#define	umtx_xtimex32	umtx_time32
+#endif
+
 struct umtx_time32 {
 	struct	timespec32	timeout;
 	uint32_t		flags;
@@ -4155,12 +4185,12 @@
 };
 
 static inline int
-umtx_copyin_timeout32(const void *addr, struct timespec *tsp)
+umtx_copyin_timeouti386(const void *addr, struct timespec *tsp)
 {
-	struct timespec32 ts32;
+	struct timespeci386 ts32;
 	int error;
 
-	error = copyin(addr, &ts32, sizeof(struct timespec32));
+	error = copyin(addr, &ts32, sizeof(struct timespeci386));
 	if (error == 0) {
 		if (ts32.tv_sec < 0 ||
 		    ts32.tv_nsec >= 1000000000 ||
@@ -4175,17 +4205,63 @@
 }
 
 static inline int
-umtx_copyin_umtx_time32(const void *addr, size_t size, struct _umtx_time *tp)
+umtx_copyin_umtx_timei386(const void *addr, size_t size, struct _umtx_time *tp)
 {
-	struct umtx_time32 t32;
+	struct umtx_timei386 t32;
 	int error;
 
 	t32.clockid = CLOCK_REALTIME;
 	t32.flags   = 0;
-	if (size <= sizeof(struct timespec32))
-		error = copyin(addr, &t32.timeout, sizeof(struct timespec32));
-	else
-		error = copyin(addr, &t32, sizeof(struct umtx_time32));
+	if (size <= sizeof(struct timespeci386)) {
+		error = copyin(addr, &t32.timeout, sizeof(struct timespeci386));
+	} else {
+		error = copyin(addr, &t32, sizeof(struct umtx_timei386));
+	}
+	if (error != 0)
+		return (error);
+	if (t32.timeout.tv_sec < 0 ||
+	    t32.timeout.tv_nsec >= 1000000000 || t32.timeout.tv_nsec < 0)
+		return (EINVAL);
+	tp->_timeout.tv_sec = t32.timeout.tv_sec;
+	tp->_timeout.tv_nsec = t32.timeout.tv_nsec;
+	tp->_flags = t32.flags;
+	tp->_clockid = t32.clockid;
+	return (0);
+}
+
+static inline int
+umtx_copyin_timeoutx32(const void *addr, struct timespec *tsp)
+{
+	struct timespecx32 ts32;
+	int error;
+
+	error = copyin(addr, &ts32, sizeof(struct timespecx32));
+	if (error == 0) {
+		if (ts32.tv_sec < 0 ||
+		    ts32.tv_nsec >= 1000000000 ||
+		    ts32.tv_nsec < 0)
+			error = EINVAL;
+		else {
+			tsp->tv_sec = ts32.tv_sec;
+			tsp->tv_nsec = ts32.tv_nsec;
+		}
+	}
+	return (error);
+}
+
+static inline int
+umtx_copyin_umtx_timex32(const void *addr, size_t size, struct _umtx_time *tp)
+{
+	struct umtx_timex32 t32;
+	int error;
+
+	t32.clockid = CLOCK_REALTIME;
+	t32.flags   = 0;
+	if (size <= sizeof(struct timespecx32)) {
+		error = copyin(addr, &t32.timeout, sizeof(struct timespecx32));
+	} else {
+		error = copyin(addr, &t32, sizeof(struct umtx_timex32));
+	}
 	if (error != 0)
 		return (error);
 	if (t32.timeout.tv_sec < 0 ||
@@ -4218,9 +4294,23 @@
 }
 
 static int
-umtx_copyout_timeout32(void *addr, size_t sz, struct timespec *tsp)
+umtx_copyout_timeoutx32(void *addr, size_t sz, struct timespec *tsp)
 {
-	struct timespec32 remain32 = {
+	struct timespecx32 remain32 = {
+		.tv_sec = tsp->tv_sec,
+		.tv_nsec = tsp->tv_nsec,
+	};
+
+	KASSERT(sz >= sizeof(struct timespec32),
+	    ("_umtx_copyops specifies incorrect sizes"));
+
+	return (copyout(&remain32, addr, sizeof(struct timespec32)));
+}
+
+static int
+umtx_copyout_timeouti386(void *addr, size_t sz, struct timespec *tsp)
+{
+	struct timespeci386 remain32 = {
 		.tv_sec = tsp->tv_sec,
 		.tv_nsec = tsp->tv_nsec,
 	};
@@ -4280,15 +4370,32 @@
 };
 
 #ifdef NEED_UMTX32
-struct _umtx_copyops umtx_native_ops32 = {
-	.copyin_timeout = umtx_copyin_timeout32,
-	.copyin_umtx_time = umtx_copyin_umtx_time32,
+struct _umtx_copyops umtx_native_opsx32 = {
+	.copyin_timeout = umtx_copyin_timeoutx32,
+	.copyin_umtx_time = umtx_copyin_umtx_timex32,
 	.copyin_robust_lists = umtx_copyin_robust_lists32,
-	.copyout_timeout = umtx_copyout_timeout32,
-	.timespec_sz = sizeof(struct timespec32),
-	.umtx_time_sz = sizeof(struct umtx_time32),
+	.copyout_timeout = umtx_copyout_timeoutx32,
+	.timespec_sz = sizeof(struct timespecx32),
+	.umtx_time_sz = sizeof(struct umtx_timex32),
 };
-#endif
+
+struct _umtx_copyops umtx_native_opsi386 = {
+	.copyin_timeout = umtx_copyin_timeouti386,
+	.copyin_umtx_time = umtx_copyin_umtx_timei386,
+	.copyin_robust_lists = umtx_copyin_robust_lists32,
+	.copyout_timeout = umtx_copyout_timeouti386,
+	.timespec_sz = sizeof(struct timespeci386),
+	.umtx_time_sz = sizeof(struct umtx_timei386),
+};
+
+#ifdef __amd64__
+#define	umtx_native_ops32	umtx_native_opsi386
+#else
+#define	umtx_native_ops32	umtx_native_opsx86
+#endif	/* __amd64__ */
+#endif	/* NEED_UMTX32 */
+
+#define	UMTX_OP__FLAGS	(UMTX_OP__32BIT | UMTX_OP__32BIT_I386)
 
 static int
 kern__umtx_op(struct thread *td, void *obj, int op, unsigned long val,
@@ -4296,7 +4403,7 @@
 {
 	struct _umtx_op_args uap = {
 		.obj = obj,
-		.op = op,
+		.op = op & ~UMTX_OP__FLAGS,
 		.val = val,
 		.uaddr1 = uaddr1,
 		.uaddr2 = uaddr2
@@ -4313,6 +4420,18 @@
 	struct _umtx_copyops *umtx_ops;
 
 	umtx_ops = &umtx_native_ops;
+#ifdef __LP64__
+	if ((uap->op & UMTX_OP__32BIT) != 0) {
+		if ((uap->op & UMTX_OP__32BIT_I386) != 0)
+			umtx_ops = &umtx_native_opsi386;
+		else
+			umtx_ops = &umtx_native_opsx32;
+	}
+#else
+	/* We consider UMTX_OP__32BIT a nop on ILP32. */
+	if ((uap->op & UMTX_OP__32BIT_I386) != 0)
+		umtx_ops = &umtx_native_opsi386;
+#endif
 	return (kern__umtx_op(td, uap->obj, uap->op, uap->val, uap->uaddr1,
 	    uap->uaddr2, umtx_ops));
 }
Index: sys/sys/umtx.h
===================================================================
--- sys/sys/umtx.h
+++ sys/sys/umtx.h
@@ -101,6 +101,9 @@
 #define	UMTX_OP_SHM		25
 #define	UMTX_OP_ROBUST_LISTS	26
 
+#define	UMTX_OP__32BIT		0x80000000
+#define	UMTX_OP__32BIT_I386	0x40000000
+
 /* Flags for UMTX_OP_CV_WAIT */
 #define	CVWAIT_CHECK_UNPARKING	0x01
 #define	CVWAIT_ABSTIME		0x02