From d28cd672a56342e4dcdbb51fe63a13e61eeefdd4 Mon Sep 17 00:00:00 2001
From: Richard Braun <rbraun@sceen.net>
Date: Fri, 17 Mar 2017 21:16:37 +0100
Subject: kern/semaphore: new module

---
 kern/semaphore.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 kern/semaphore.c

(limited to 'kern/semaphore.c')

diff --git a/kern/semaphore.c b/kern/semaphore.c
new file mode 100644
index 00000000..e41e2c2f
--- /dev/null
+++ b/kern/semaphore.c
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#include <kern/semaphore.h>
+#include <kern/semaphore_i.h>
+#include <kern/sleepq.h>
+
+void
+semaphore_wait_slow(struct semaphore *semaphore)
+{
+    struct sleepq *sleepq;
+    unsigned int prev;
+
+    sleepq = sleepq_lend(semaphore, false);
+
+    for (;;) {
+        prev = semaphore_dec(semaphore);
+
+        if (prev != 0) {
+            break;
+        }
+
+        sleepq_wait(sleepq, "sem");
+    }
+
+    sleepq_return(sleepq);
+}
+
+void
+semaphore_post_slow(struct semaphore *semaphore)
+{
+    struct sleepq *sleepq;
+
+    sleepq = sleepq_acquire(semaphore, false);
+
+    if (sleepq == NULL) {
+        return;
+    }
+
+    sleepq_signal(sleepq);
+
+    sleepq_release(sleepq);
+}
-- 
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