From 87e3cde79b75b143f59ea2ae1325de19ee6e87ab Mon Sep 17 00:00:00 2001
From: Ali Mashtizadeh <mashti@cs.stanford.edu>
Date: Sun, 1 Feb 2015 19:21:16 -0800
Subject: [PATCH] pthread condition variable implementation

---
 lib/libc/posix/pthread.c | 84 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 78 insertions(+), 6 deletions(-)

diff --git a/lib/libc/posix/pthread.c b/lib/libc/posix/pthread.c
index 532f6f0..cc9199c 100644
--- a/lib/libc/posix/pthread.c
+++ b/lib/libc/posix/pthread.c
@@ -301,40 +301,112 @@ pthread_mutex_unlock(pthread_mutex_t *mutex)
  * Condition Variables
  */
 
-struct pthread_cond {
+struct pthread_condattr {
+    uint64_t	_unused;
 };
 
-struct pthread_condattr {
+struct pthread_cond {
+    CoreMutex	mtx;
+    uint64_t	enter;
+    uint64_t	exit;
 };
 
 int
 pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
 {
-    return EINVAL;
+    struct pthread_cond *cnd = (struct pthread_cond *)malloc(sizeof(*cnd));
+
+    if (cnd == NULL) {
+	return ENOMEM;
+    }
+
+    CoreMutex_Init(&cnd->mtx);
+    cnd->enter = 0;
+    cnd->exit = 0;
+
+    *cond = cnd;
+
+    return 0;
 }
 
 int
 pthread_cond_destroy(pthread_cond_t *cond)
 {
+    struct pthread_cond *cnd = *cond;
+
+    *cond = NULL;
+    free(cnd);
+
     return EINVAL;
 }
 
 int
 pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 {
-    return EINVAL;
+    struct pthread_cond *cnd;
+    uint64_t level;
+
+    if (*cond == NULL) {
+	int status = pthread_cond_init(cond, NULL);
+	if (status != 0)
+	    return status;
+    }
+    cnd = *cond;
+
+    if (mutex)
+	pthread_mutex_unlock(mutex);
+
+    CoreMutex_Lock(&cnd->mtx);
+    level = cnd->enter;
+    cnd->enter++;
+    CoreMutex_Unlock(&cnd->mtx);
+
+    while (level >= cnd->exit) {
+	OSThreadSleep(0);
+    }
+
+    if (mutex)
+	pthread_mutex_lock(mutex);
+
+    return 0;
 }
 
 
 int
 pthread_cond_signal(pthread_cond_t *cond)
 {
-    return EINVAL;
+    struct pthread_cond *cnd;
+
+    if (*cond == NULL) {
+	int status = pthread_cond_init(cond, NULL);
+	if (status != 0)
+	    return status;
+    }
+    cnd = *cond;
+
+    CoreMutex_Lock(&cnd->mtx);
+    cnd->exit++;
+    CoreMutex_Unlock(&cnd->mtx);
+
+    return 0;
 }
 
 int
 pthread_cond_broadcast(pthread_cond_t *cond)
 {
-    return EINVAL;
+    struct pthread_cond *cnd;
+
+    if (*cond == NULL) {
+	int status = pthread_cond_init(cond, NULL);
+	if (status != 0)
+	    return status;
+    }
+    cnd = *cond;
+
+    CoreMutex_Lock(&cnd->mtx);
+    cnd->exit = cnd->enter;
+    CoreMutex_Unlock(&cnd->mtx);
+
+    return 0;
 }