From 0e2552ac5554e69d04bad03d19794b8d8eeaed76 Mon Sep 17 00:00:00 2001
From: Remzi Arpaci-Dusseau <remzi.arpacidusseau@gmail.com>
Date: Tue, 30 Apr 2019 09:57:31 -0500
Subject: [PATCH] no lock while signalling

---
 threads-cv/Makefile       |  1 +
 threads-cv/join_no_lock.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 threads-cv/join_no_lock.c

diff --git a/threads-cv/Makefile b/threads-cv/Makefile
index b83ce38..6b5378b 100644
--- a/threads-cv/Makefile
+++ b/threads-cv/Makefile
@@ -3,6 +3,7 @@ CFLAGS := -Wall -Werror -I../include
 
 SRCS   := join.c \
 	join_spin.c \
+	join_no_lock.c \
 	join_modular.c
 
 OBJS   := ${SRCS:c=o}
diff --git a/threads-cv/join_no_lock.c b/threads-cv/join_no_lock.c
new file mode 100644
index 0000000..2272db7
--- /dev/null
+++ b/threads-cv/join_no_lock.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <pthread.h>
+#include "common.h"
+#include "common_threads.h"
+
+pthread_cond_t  c = PTHREAD_COND_INITIALIZER;
+pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
+int done = 0;
+
+void *child(void *arg) {
+    printf("child: begin\n");
+    sleep(1);
+    done = 1;
+    printf("child: signal\n");
+    Cond_signal(&c);
+    return NULL;
+}
+int main(int argc, char *argv[]) {
+    pthread_t p;
+    printf("parent: begin\n");
+    Pthread_create(&p, NULL, child, NULL);
+    Mutex_lock(&m);
+    printf("parent: check condition\n");
+    while (done == 0) {
+	sleep(2);
+	printf("parent: wait to be signalled...\n");
+	Cond_wait(&c, &m); 
+    }
+    Mutex_unlock(&m);
+    printf("parent: end\n");
+    return 0;
+}
+