From 4278f99adcbcfbd52904c0d8809184afe091c958 Mon Sep 17 00:00:00 2001
From: Agustina Arzille <avarzille@riseup.net>
Date: Fri, 21 Jul 2017 00:49:39 +0200
Subject: Rework mutex implementation selection

---
 kern/mutex/mutex_plain.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 kern/mutex/mutex_plain.c

(limited to 'kern/mutex/mutex_plain.c')

diff --git a/kern/mutex/mutex_plain.c b/kern/mutex/mutex_plain.c
new file mode 100644
index 00000000..a925a5a2
--- /dev/null
+++ b/kern/mutex/mutex_plain.c
@@ -0,0 +1,65 @@
+/*
+ * 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/atomic.h>
+#include <kern/mutex.h>
+#include <kern/mutex_types.h>
+#include <kern/sleepq.h>
+
+void
+mutex_plain_lock_slow(struct mutex *mutex)
+{
+    unsigned int state;
+    struct sleepq *sleepq;
+    unsigned long flags;
+
+    sleepq = sleepq_lend(mutex, false, &flags);
+
+    for (;;) {
+        state = atomic_swap_release(&mutex->state, MUTEX_CONTENDED);
+
+        if (state == MUTEX_UNLOCKED) {
+            break;
+        }
+
+        sleepq_wait(sleepq, "mutex");
+    }
+
+    if (sleepq_empty(sleepq)) {
+        /* TODO Review memory order */
+        atomic_store(&mutex->state, MUTEX_LOCKED, ATOMIC_RELEASE);
+    }
+
+    sleepq_return(sleepq, flags);
+}
+
+void
+mutex_plain_unlock_slow(struct mutex *mutex)
+{
+    struct sleepq *sleepq;
+    unsigned long flags;
+
+    sleepq = sleepq_acquire(mutex, false, &flags);
+
+    if (sleepq != NULL) {
+        sleepq_signal(sleepq);
+        sleepq_release(sleepq, flags);
+    }
+}
-- 
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