From 2fdcc4b5574eae39d2ce78370d0361698f5bf63e Mon Sep 17 00:00:00 2001
From: Ali Mashtizadeh <mashti@cs.stanford.edu>
Date: Fri, 30 Jan 2015 18:40:25 -0800
Subject: [PATCH] pthread_mutex implementation

---
 include/errno.h          |   1 +
 include/pthread.h        |  11 ++++
 lib/libc/posix/pthread.c | 115 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)

diff --git a/include/errno.h b/include/errno.h
index 3c6db71..4c2d3c3 100644
--- a/include/errno.h
+++ b/include/errno.h
@@ -12,6 +12,7 @@
 #define ENAMETOOLONG	0xBAD8
 #define ENOSYS		0xBAD9
 #define EAGAIN		0xBADA
+#define EBUSY		0xBADB
 
 #endif /* __ERRNO_H__ */
 
diff --git a/include/pthread.h b/include/pthread.h
index 7433701..59e9825 100644
--- a/include/pthread.h
+++ b/include/pthread.h
@@ -2,12 +2,17 @@
 #ifndef __PTHREAD_H__
 #define __PTHREAD_H__
 
+#define PTHREAD_MUTEX_INITIALIZER	NULL
+#define PTHREAD_COND_INITIALIZER	NULL
+
 typedef struct pthread *pthread_t;
 typedef struct pthread_attr *pthread_attr_t;
 typedef struct pthread_barrier *pthread_barrier_t;
 typedef struct pthread_barrierattr *pthread_barrierattr_t;
 typedef struct pthread_mutex *pthread_mutex_t;
 typedef struct pthread_mutexattr *pthread_mutexattr_t;
+typedef struct pthread_cond *pthread_cond_t;
+typedef struct pthread_condattr *pthread_condattr_t;
 
 pthread_t pthread_self(void);
 int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
@@ -45,5 +50,11 @@ int pthread_mutex_unlock(pthread_mutex_t *mutex);
  * Condition Variables
  */
 
+int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
+int pthread_cond_destroy(pthread_cond_t *cond);
+int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);
+int pthread_cond_signal(pthread_cond_t *cond);
+int pthread_cond_broadcast(pthread_cond_t *cond);
+
 #endif /* __PTHREAD_H__ */
 
diff --git a/lib/libc/posix/pthread.c b/lib/libc/posix/pthread.c
index 8b89873..0631ad6 100644
--- a/lib/libc/posix/pthread.c
+++ b/lib/libc/posix/pthread.c
@@ -113,45 +113,123 @@ pthread_barrier_init(pthread_barrier_t *barrier,
 		     const pthread_barrierattr_t *attr,
 		     unsigned count)
 {
+    return EINVAL;
 }
 
 int
 pthread_barrier_destroy(pthread_barrier_t *barrier)
 {
+    return EINVAL;
 }
 
 int
 pthread_barrier_wait(pthread_barrier_t *barrier)
 {
+    return EINVAL;
 }
 
 /*
  * Mutex
  */
 
+struct pthread_mutexattr {
+    uint64_t	_unused;
+};
+
+struct pthread_mutex {
+    uint64_t	lock;
+};
+
 int
 pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
 {
+    struct pthread_mutex *mtx = (struct pthread_mutex *)malloc(sizeof(*mtx));
+
+    if (mtx == NULL) {
+	return ENOMEM;
+    }
+
+    mtx->lock = 0;
+    *mutex = mtx;
+
+    return 0;
 }
 
 int
 pthread_mutex_destroy(pthread_mutex_t *mutex)
 {
+    struct pthread_mutex *mtx = *mutex;
+
+    if (mtx == NULL) {
+	return EINVAL;
+    } else if (mtx->lock == 1) {
+	return EBUSY;
+    } else {
+	*mutex = NULL;
+	free(mtx);
+	return 0;
+    }
 }
 
 int
 pthread_mutex_lock(pthread_mutex_t *mutex)
 {
+    struct pthread_mutex *mtx;
+    
+    if (*mutex == NULL) {
+	int status = pthread_mutex_init(mutex, NULL);
+	if (status != 0)
+	    return status;
+    }
+
+    mtx = *mutex;
+
+    // XXX: Should have the kernel wait kernel instead of yielding
+    while (__sync_lock_test_and_set(&mtx->lock, 1) == 1) {
+	OSThreadSleep(0);
+    }
+
+    return 0;
 }
 
 int
 pthread_mutex_trylock(pthread_mutex_t *mutex)
 {
+    struct pthread_mutex *mtx;
+
+    if (*mutex == NULL) {
+	int status = pthread_mutex_init(mutex, NULL);
+	if (status != 0)
+	    return status;
+    }
+
+    mtx = *mutex;
+
+    if (__sync_lock_test_and_set(&mtx->lock, 1) == 1) {
+	return EBUSY;
+    } else {
+	// Lock acquired
+	return 0;
+    }
 }
 
 int
 pthread_mutex_unlock(pthread_mutex_t *mutex)
 {
+    struct pthread_mutex *mtx;
+
+    if (*mutex == NULL) {
+	int status = pthread_mutex_init(mutex, NULL);
+	if (status != 0)
+	    return status;
+    }
+
+    mtx = *mutex;
+
+    __sync_lock_release(&mtx->lock);
+    // XXX: Wakeup a sleeping thread
+
+    return 0;
 }
 
 
@@ -163,3 +241,40 @@ pthread_mutex_unlock(pthread_mutex_t *mutex)
  * Condition Variables
  */
 
+struct pthread_cond {
+};
+
+struct pthread_condattr {
+};
+
+int
+pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
+{
+    return EINVAL;
+}
+
+int
+pthread_cond_destroy(pthread_cond_t *cond)
+{
+    return EINVAL;
+}
+
+int
+pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
+{
+    return EINVAL;
+}
+
+
+int
+pthread_cond_signal(pthread_cond_t *cond)
+{
+    return EINVAL;
+}
+
+int
+pthread_cond_broadcast(pthread_cond_t *cond)
+{
+    return EINVAL;
+}
+