From 3a809b9faadfd0a8d898aede15cabfd24ee1a13f Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 3 Jul 2025 18:20:22 -0400
Subject: kernel: synch: Add mutual exclusion locks

Add mutex locks, these differ from spinlocks as they are named and also
yield to the scheduler instead of just spinning if the lock is acquired.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/kern/kern_synch.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

(limited to 'sys/kern/kern_synch.c')

diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 57b27d0..0d36d7f 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -28,12 +28,15 @@
  */
 
 #include <sys/types.h>
+#include <sys/mutex.h>
 #include <sys/systm.h>
 #include <sys/errno.h>
+#include <sys/sched.h>
 #include <sys/atomic.h>
 #include <sys/syslog.h>
 #include <sys/spinlock.h>
 #include <dev/timer.h>
+#include <string.h>
 
 #define pr_trace(fmt, ...) kprintf("synch: " fmt, ##__VA_ARGS__)
 #define pr_error(...) pr_trace(__VA_ARGS__)
@@ -136,3 +139,57 @@ sysrel(void)
 {
     spinlock_release(&__syslock);
 }
+
+/*
+ * Create a new mutex lock object
+ */
+struct mutex *
+mutex_new(const char *name)
+{
+    struct mutex *mtx;
+    size_t namelen;
+
+    mtx = dynalloc(sizeof(*mtx));
+    if (mtx == NULL) {
+        return NULL;
+    }
+
+    mtx->lock = 0;
+    namelen = strlen(name);
+
+    /* Don't overflow the name buffer */
+    if (namelen >= MUTEX_NAME_LEN) {
+        namelen = MUTEX_NAME_LEN - 1;
+    }
+
+    memcpy(mtx->name, name, namelen);
+    return mtx;
+}
+
+/*
+ * Acquire a mutex
+ *
+ * @mtx: Mutex to acquire
+ * @flags: Optional flags
+ */
+int
+mutex_acquire(struct mutex *mtx, int flags)
+{
+    while (__atomic_test_and_set(&mtx->lock, __ATOMIC_ACQUIRE)) {
+        sched_yield();
+    }
+
+    return 0;
+}
+
+void
+mutex_release(struct mutex *mtx)
+{
+    __atomic_clear(&mtx->lock, __ATOMIC_RELEASE);
+}
+
+void
+mutex_free(struct mutex *mtx)
+{
+    dynfree(mtx);
+}
-- 
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