From a2d7e3595dbcb4d3a9e9d046f5acd49d4e8bc87e Mon Sep 17 00:00:00 2001
From: Remzi Arpaci-Dusseau <remzi.arpacidusseau@gmail.com>
Date: Mon, 29 Apr 2019 14:39:06 -0500
Subject: [PATCH] first bits of CV code

---
 threads-cv/Makefile       | 20 +++++++++++++
 threads-cv/join.c         | 31 ++++++++++++++++++++
 threads-cv/join_modular.c | 60 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 111 insertions(+)
 create mode 100644 threads-cv/Makefile
 create mode 100644 threads-cv/join.c
 create mode 100644 threads-cv/join_modular.c

diff --git a/threads-cv/Makefile b/threads-cv/Makefile
new file mode 100644
index 0000000..0124b54
--- /dev/null
+++ b/threads-cv/Makefile
@@ -0,0 +1,20 @@
+CC     := gcc
+CFLAGS := -Wall -Werror -I../include 
+
+SRCS   := join.c \
+	join_modular.c
+
+OBJS   := ${SRCS:c=o}
+PROGS  := ${SRCS:.c=}
+
+.PHONY: all
+all: ${PROGS}
+
+${PROGS} : % : %.o Makefile
+	${CC} $< -o $@ -pthread
+
+clean:
+	rm -f ${PROGS} ${OBJS}
+
+%.o: %.c Makefile
+	${CC} ${CFLAGS} -c $<
diff --git a/threads-cv/join.c b/threads-cv/join.c
new file mode 100644
index 0000000..af1d883
--- /dev/null
+++ b/threads-cv/join.c
@@ -0,0 +1,31 @@
+#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\n");
+    sleep(1);
+    Mutex_lock(&m);
+    done = 1;
+    Cond_signal(&c);
+    Mutex_unlock(&m);
+    return NULL;
+}
+int main(int argc, char *argv[]) {
+    pthread_t p;
+    printf("parent: begin\n");
+    Pthread_create(&p, NULL, child, NULL);
+    Mutex_lock(&m);
+    while (done == 0) 
+	Cond_wait(&c, &m); // releases lock when going to sleep
+    Mutex_unlock(&m);
+    printf("parent: end\n");
+    return 0;
+}
+
diff --git a/threads-cv/join_modular.c b/threads-cv/join_modular.c
new file mode 100644
index 0000000..5cfc101
--- /dev/null
+++ b/threads-cv/join_modular.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <pthread.h>
+#include "common.h"
+#include "common_threads.h"
+
+//
+// Simple sync "object"
+//
+
+typedef struct {
+    pthread_cond_t c;
+    pthread_mutex_t m;
+    int done;
+} synchronizer_t;
+
+synchronizer_t s;
+
+void sync_init(synchronizer_t *s) {
+    s->done = 0;
+    Mutex_init(&s->m);
+    Cond_init(&s->c);
+}
+
+void sync_signal(synchronizer_t *s) {
+    Mutex_lock(&s->m);
+    s->done = 1;
+    Cond_signal(&s->c);
+    Mutex_unlock(&s->m);
+}
+
+void sync_wait(synchronizer_t *s) {
+    Mutex_lock(&s->m);
+    while (s->done == 0) 
+	Cond_wait(&s->c, &s->m); 
+    s->done = 0; // reset for next use
+    Mutex_unlock(&s->m);
+}
+
+
+//
+// Main threads
+//
+
+void *child(void *arg) {
+    printf("child\n");
+    sleep(1);
+    sync_signal(&s);
+    return NULL;
+}
+int main(int argc, char *argv[]) {
+    pthread_t p;
+    printf("parent: begin\n");
+    sync_init(&s);
+    Pthread_create(&p, NULL, child, NULL);
+    sync_wait(&s);
+    printf("parent: end\n");
+    return 0;
+}
+