1 files changed, 11 insertions, 1 deletions

diff --git a/lib/libc_r/uthread/uthread_fork.c b/lib/libc_r/uthread/uthread_fork.c
index 97039b3ef804..9fc17c6e4754 100644
--- a/lib/libc_r/uthread/uthread_fork.c
+++ b/lib/libc_r/uthread/uthread_fork.c
@@ -32,6 +32,7 @@
  * $FreeBSD$
  */
 #include <errno.h>
+#include <signal.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -108,7 +109,16 @@ _fork(void)
 		else if (_pq_init(&_readyq) != 0) {
 			/* Abort this application: */
 			PANIC("Cannot initialize priority ready queue.");
-		} else {
+		} else if ((_thread_sigstack.ss_sp == NULL) &&
+		    ((_thread_sigstack.ss_sp = malloc(SIGSTKSZ)) == NULL))
+			PANIC("Unable to allocate alternate signal stack");
+		else {
+			/* Install the alternate signal stack: */
+			_thread_sigstack.ss_size = SIGSTKSZ;
+			_thread_sigstack.ss_flags = 0;
+			if (_thread_sys_sigaltstack(&_thread_sigstack, NULL) != 0)
+				PANIC("Unable to install alternate signal stack");
+
 			/*
 			 * Enter a loop to remove all threads other than
 			 * the running thread from the thread list: