diff --git a/lib/libc/gen/sleep.c b/lib/libc/gen/sleep.c
index 87aeb366bc5e..b3dd8b72c025 100644
--- a/lib/libc/gen/sleep.c
+++ b/lib/libc/gen/sleep.c
@@ -38,19 +38,80 @@ static char sccsid[] = "@(#)sleep.c	8.1 (Berkeley) 6/4/93";
 #include <sys/time.h>
 #include <signal.h>
 #include <unistd.h>
+#ifdef  _THREAD_SAFE
+#include <pthread.h>
+#include "pthread_private.h"
+#else
+
+#define	setvec(vec, a) \
+	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0
+
+static int ringring;
+#endif
 
 unsigned int
 sleep(seconds)
 	unsigned int seconds;
 {
-	struct timespec time_to_sleep;
-	struct timespec time_remaining;
+#ifdef  _THREAD_SAFE
+    struct timespec time_to_sleep;
+    struct timespec time_remaining;
 
-	if (seconds != 0) {
-		time_to_sleep.tv_sec = seconds;
-		time_to_sleep.tv_nsec = 0;
-		nanosleep(&time_to_sleep, &time_remaining);
-		seconds = time_remaining.tv_sec;
+    if (seconds) {
+        time_to_sleep.tv_sec = seconds;
+        time_to_sleep.tv_nsec = 0;
+        nanosleep(&time_to_sleep,&time_remaining);
+        seconds = time_remaining.tv_sec;
+    }
+    return(seconds);
+#else
+	register struct itimerval *itp;
+	struct itimerval itv, oitv;
+	struct sigvec vec, ovec;
+	long omask;
+	static void sleephandler();
+
+	itp = &itv;
+	if (!seconds)
+		return 0;
+	timerclear(&itp->it_interval);
+	timerclear(&itp->it_value);
+	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
+		return seconds;
+	itp->it_value.tv_sec = seconds;
+	if (timerisset(&oitv.it_value)) {
+		if (timercmp(&oitv.it_value, &itp->it_value, >))
+			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
+		else {
+			itp->it_value = oitv.it_value;
+			/*
+			 * This is a hack, but we must have time to return
+			 * from the setitimer after the alarm or else it'll
+			 * be restarted.  And, anyway, sleep never did
+			 * anything more than this before.
+			 */
+			oitv.it_value.tv_sec = 1;
+			oitv.it_value.tv_usec = 0;
+		}
 	}
-	return (seconds);
+	setvec(vec, sleephandler);
+	(void) sigvec(SIGALRM, &vec, &ovec);
+	omask = sigblock(sigmask(SIGALRM));
+	ringring = 0;
+	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
+	while (!ringring)
+		sigpause(omask &~ sigmask(SIGALRM));
+	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
+	(void) sigsetmask(omask);
+	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
+	return 0;
+#endif
 }
+
+#ifndef  _THREAD_SAFE
+static void
+sleephandler()
+{
+	ringring = 1;
+}
+#endif