1 files changed, 108 insertions, 0 deletions
diff --git a/user/libthread/cond.c b/user/libthread/cond.c
new file mode 100644
index 0000000..ccc7767
--- /dev/null
+++ b/user/libthread/cond.c
@@ -0,0 +1,108 @@
+/**
+ * @file cond.c
+ * @author Hanjie Wu (hanjiew)
+ * @author Devang Acharya (devanga)
+ * @brief
+ * @date 2023-02-22
+ *
+ */
+
+#include <assert.h>
+#include <cond.h>
+#include <stdlib.h>
+#include <syscall.h>
+
+/**
+ * @brief initialize the condition variable pointed by cv
+ *
+ * @param cv
+ * @return 0
+ */
+int cond_init(cond_t* cv) {
+    mutex_init(&cv->lock);
+    cv->queue = NULL;
+    return 0;
+}
+
+/**
+ * @brief destroy the condition variable pointed by cv.
+ *
+ * @param cv
+ */
+void cond_destroy(cond_t* cv) {
+    affirm(cv->queue == NULL);
+    mutex_destroy(&cv->lock);
+}
+
+/**
+ * @brief wait on a cv until signaled and lock mp
+ *
+ * @param cv
+ */
+void cond_wait(cond_t* cv, mutex_t* mp) {
+    cond_node_t self;
+    mutex_lock(&cv->lock);
+    self.tid = gettid();
+    self.signaled = 0;
+    if (cv->queue == NULL) { /* add self node to wait list */
+        cv->queue = &self;
+        self.next = self.prev = &self;
+    } else {
+        self.next = cv->queue;
+        self.prev = cv->queue->prev;
+        cv->queue->prev->next = &self;
+        cv->queue->prev = &self;
+    }
+    mutex_unlock(mp);
+    mutex_unlock(&cv->lock);
+    while (self.signaled != 1) {
+        deschedule(&self.signaled); /* will be set to 1 after other thread
+                                       signal the cv */
+    }
+    mutex_lock(mp);
+}
+
+/**
+ * @brief signal a cv and wake up one thread
+ *
+ * @param cv
+ */
+void cond_signal(cond_t* cv) {
+    mutex_lock(&cv->lock);
+    if (cv->queue != NULL) { /* remove a waiter from the list */
+        cond_node_t* p = cv->queue;
+        if (p->next == p) {
+            cv->queue = NULL;
+        } else {
+            cv->queue = p->next;
+            p->next->prev = p->prev;
+            p->prev->next = p->next;
+        }
+        int tid = p->tid;
+        p->signaled = 1;
+        make_runnable(tid);
+    }
+    mutex_unlock(&cv->lock);
+}
+
+/**
+ * @brief signal a cv and wake up all threads
+ *
+ * @param cv
+ */
+void cond_broadcast(cond_t* cv) {
+    mutex_lock(&cv->lock);
+    cond_node_t* p = cv->queue;
+    if (p != NULL) {
+        cond_node_t* end = p;
+        do {
+            cond_node_t* q = p->next;
+            int tid = p->tid;
+            p->signaled = 1;
+            make_runnable(tid);
+            p = q;
+        } while (p != end);
+        cv->queue = NULL;
+    }
+    mutex_unlock(&cv->lock);
+}