From a3eba19470c09f42272dac5ca1a34bd8a5cbe834 Mon Sep 17 00:00:00 2001
From: Zheng Da <zhengda1936@gmail.com>
Date: Tue, 17 Nov 2009 10:26:25 +0100
Subject: The original version of DDEKit.

---
 libddekit/condvar.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 libddekit/condvar.c

(limited to 'libddekit/condvar.c')

diff --git a/libddekit/condvar.c b/libddekit/condvar.c
new file mode 100644
index 00000000..a495cf92
--- /dev/null
+++ b/libddekit/condvar.c
@@ -0,0 +1,108 @@
+/**
+ * Unchecked (no BSD invariants) condition variable implementation for
+ * dde-internal use. Written from scratch.
+ *
+ * \author Thomas Friebel <tf13@os.inf.tu-dresden.de>
+ */
+#include <l4/dde/ddekit/condvar.h>
+#include <l4/dde/ddekit/lock.h>
+#include <l4/dde/ddekit/memory.h>
+
+#include <l4/log/l4log.h>
+#include <l4/semaphore/semaphore.h>
+#include <l4/lock/lock.h>
+
+struct ddekit_condvar {
+	unsigned waiters;
+	unsigned signals;
+	l4lock_t lock;
+	l4semaphore_t sem;
+	l4semaphore_t handshake;
+};
+
+ddekit_condvar_t *ddekit_condvar_init() {
+	ddekit_condvar_t *cvp;
+
+	cvp = ddekit_simple_malloc(sizeof(*cvp));
+
+	cvp->waiters   = 0;
+	cvp->signals   = 0;
+	cvp->lock      = L4LOCK_UNLOCKED;
+	cvp->sem       = L4SEMAPHORE_INIT(0);
+	cvp->handshake = L4SEMAPHORE_INIT(0);
+
+	return cvp;
+}
+
+void ddekit_condvar_wait(ddekit_condvar_t *cvp, ddekit_lock_t *mp) {
+	ddekit_condvar_wait_timed(cvp, mp, -1);
+}
+
+int ddekit_condvar_wait_timed(ddekit_condvar_t *cvp, ddekit_lock_t *mp, int timo) {
+	int rval;
+
+	l4lock_lock(&cvp->lock);
+	cvp->waiters++;
+	l4lock_unlock(&cvp->lock);
+
+	ddekit_lock_unlock(mp);
+
+	if (timo == -1) {
+		l4semaphore_down(&cvp->sem);
+		rval = 0;
+	} else {
+		rval = l4semaphore_down_timed(&cvp->sem, timo);
+	}
+
+	l4lock_lock(&cvp->lock);
+	if (cvp->signals > 0) {
+		/* if we timed out, but there is a signal now, consume it */
+		if (rval) l4semaphore_down(&cvp->sem);
+
+		l4semaphore_up(&cvp->handshake);
+		cvp->signals--;
+	}
+	cvp->waiters--;
+	l4lock_unlock(&cvp->lock);
+
+	ddekit_lock_lock(mp);
+
+	return rval;
+}
+
+void ddekit_condvar_signal(ddekit_condvar_t *cvp)
+{
+	l4lock_lock(&cvp->lock);
+
+	if (cvp->waiters > cvp->signals) {
+		cvp->signals++;
+		l4semaphore_up(&cvp->sem);
+		l4lock_unlock(&cvp->lock);
+		l4semaphore_down(&cvp->handshake);
+	} else {
+		/* nobody left to wakeup */
+		l4lock_unlock(&cvp->lock);
+	}
+}
+
+void ddekit_condvar_broadcast(ddekit_condvar_t *cvp) {
+	int waiters;
+
+	l4lock_lock(&cvp->lock);
+
+	waiters = cvp->waiters - cvp->signals;
+	if (waiters > 0) {
+		int i;
+
+		cvp->signals = cvp->waiters;
+		for (i=0; i<waiters; i++) {
+			l4semaphore_up(&cvp->sem);
+		}
+		l4lock_unlock(&cvp->lock);
+		for (i=0; i<waiters; i++) {
+			l4semaphore_down(&cvp->handshake);
+		}
+	} else {
+		l4lock_unlock(&cvp->lock);
+	}
+}
-- 
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