diff --git a/sys/kern/kern_thr.c b/sys/kern/kern_thr.c
index bcbe1685c4c1..de45d0a487c5 100644
--- a/sys/kern/kern_thr.c
+++ b/sys/kern/kern_thr.c
@@ -53,6 +53,8 @@ __FBSDID("$FreeBSD$");
 
 #include <machine/frame.h>
 
+#include <security/audit/audit.h>
+
 #ifdef COMPAT_IA32
 
 extern struct sysentvec ia32_freebsd_sysvec;
@@ -336,6 +338,59 @@ thr_kill(struct thread *td, struct thr_kill_args *uap)
 	return (error);
 }
 
+int
+thr_kill2(struct thread *td, struct thr_kill2_args *uap)
+    /* pid_t pid, long id, int sig */
+{
+	struct thread *ttd;
+	struct proc *p;
+	int error;
+
+	AUDIT_ARG(signum, uap->sig);
+
+	if (uap->pid == td->td_proc->p_pid) {
+		p = td->td_proc;
+		PROC_LOCK(p);
+	} else if ((p = pfind(uap->pid)) == NULL) {
+		return (ESRCH);
+	}
+	AUDIT_ARG(process, p);
+
+	error = p_cansignal(td, p, uap->sig);
+	if (error == 0) {
+		if (uap->id == -1) {
+			if (uap->sig != 0 && !_SIG_VALID(uap->sig)) {
+				error = EINVAL;
+			} else {
+				error = ESRCH;
+				FOREACH_THREAD_IN_PROC(p, ttd) {
+					if (ttd != td) {
+						error = 0;
+						if (uap->sig == 0)
+							break;
+						tdsignal(p, ttd, uap->sig, NULL);
+					}
+				}
+			}
+		} else {
+			if (uap->id != td->td_tid)
+				ttd = thread_find(p, uap->id);
+			else
+				ttd = td;
+			if (ttd == NULL)
+				error = ESRCH;
+			else if (uap->sig == 0)
+				;
+			else if (!_SIG_VALID(uap->sig))
+				error = EINVAL;
+			else
+				tdsignal(p, ttd, uap->sig, NULL);
+		}
+	}
+	PROC_UNLOCK(p);
+	return (error);
+}
+
 int
 thr_suspend(struct thread *td, struct thr_suspend_args *uap)
 	/* const struct timespec *timeout */
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index f9c784956fbb..1189f2c8ab36 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -846,5 +846,6 @@
 				    int whence); }
 479	AUE_TRUNCATE	STD	{ int truncate(char *path, off_t length); }
 480	AUE_FTRUNCATE	STD	{ int ftruncate(int fd, off_t length); }
+481	AUE_KILL	STD	{ int thr_kill2(pid_t pid, long id, int sig); }
 ; Please copy any additions and changes to the following compatability tables:
 ; sys/compat/freebsd32/syscalls.master
diff --git a/sys/sys/thr.h b/sys/sys/thr.h
index 6331a7ae9e14..ae4a65d368f2 100644
--- a/sys/sys/thr.h
+++ b/sys/sys/thr.h
@@ -30,8 +30,14 @@
 #ifndef _SYS_THR_H_
 #define	_SYS_THR_H_
 
+#include <sys/_types.h>
 #include <sys/sched.h>
 
+#ifndef _SIZE_T_DECLARED
+typedef __size_t	size_t;
+#define _SIZE_T_DECLARED
+#endif
+
 /* Create the thread in the suspended state. */
 #define	THR_SUSPENDED		0x0001
 /* Create the system scope thread. */
@@ -55,12 +61,19 @@ struct thr_param {
  * See pthread_*
  */
 #ifndef _KERNEL
+#include <sys/ucontext.h>
+
+#ifndef _PID_T_DECLARED
+typedef __pid_t		pid_t;
+#define _PID_T_DECLARED
+#endif
 
 int thr_create(ucontext_t *ctx, long *id, int flags);
 int thr_new(struct thr_param *param, int param_size);
 int thr_self(long *id);
 void thr_exit(long *state);
 int thr_kill(long id, int sig);
+int thr_kill2(pid_t pid, long id, int sig);
 int thr_suspend(const struct timespec *timeout);
 int thr_wake(long id);
 int thr_set_name(long id, const char *name);