mos: kern: Add spinlock sources

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 125 insertions, 0 deletions

diff --git a/mos/sys/inc/kern/spinlock.h b/mos/sys/inc/kern/spinlock.h
new file mode 100644
index 0000000..3168a1b
--- /dev/null
+++ b/mos/sys/inc/kern/spinlock.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef _KERN_SPINLOCK_H_
+#define _KERN_SPINLOCK_H_ 1
+
+#include <sdk/types.h>
+#include <sdk/status.h>
+#include <sdk/param.h>
+
+/* Parameters */
+#define SPINLOCK_NAMELEN 16
+
+/* Flags */
+#define SPINLOCK_IRQMUT BIT(0)      /* Mutate IRQ state */
+
+/*
+ * Represents a spinlock
+ *
+ * @name: Spinlock name
+ * @lock: Actual lock
+ */
+typedef struct {
+    char name[SPINLOCK_NAMELEN];
+    USIZE lock;
+} SPINLOCK;
+
+/*
+ * Initialize a spinlock descriptor
+ *
+ * @name: Name of spinlock
+ * @res: Result is written here
+ */
+MOS_STATUS spinlock_init(const char *name, SPINLOCK *res);
+
+/*
+ * Acquire a spinlock
+ *
+ * @lock: Lock to acquire
+ * @flags: Optional flags
+ */
+void spinlock_acquire(SPINLOCK *lock, USHORT flags);
+
+/*
+ * Release a spinlock
+ *
+ * @lock: Lock to release
+ */
+void spinlock_release(SPINLOCK *lock);
+
+#endif  /* !_KERN_SPINLOCK_H_ */
diff --git a/mos/sys/kern/kern_spinlock.c b/mos/sys/kern/kern_spinlock.c
new file mode 100644
index 0000000..aaa80de
--- /dev/null
+++ b/mos/sys/kern/kern_spinlock.c
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <sdk/types.h>
+#include <sdk/status.h>
+#include <sdk/string.h>
+#include <mu/cpu.h>
+#include <kern/spinlock.h>
+
+MOS_STATUS
+spinlock_init(const char *name, SPINLOCK *res)
+{
+    USIZE name_len;
+
+    if (name == NULL || res == NULL) {
+        return STATUS_INVALID_ARG;
+    }
+
+    name_len = strlen(name);
+    if (name_len >= SPINLOCK_NAMELEN - 1) {
+        return STATUS_NAME_TOO_LONG;
+    }
+
+    memcpy(res->name, name, name_len);
+    res->lock = 0;
+    return STATUS_SUCCESS;
+}
+
+void
+spinlock_acquire(SPINLOCK *lock, USHORT flags)
+{
+    BOOL irq_state = false;
+
+    if (lock == NULL) {
+        return;
+    }
+
+    /*
+     * Usually this should be the default but this kind of thing should
+     * be somewhat deterministic. If we are to mutate, mask the interrupts.
+     */
+    if (ISSET(flags, SPINLOCK_IRQMUT)) {
+        irq_state = mu_irq_state();
+        mu_irq_setmask(true);
+    }
+
+    /*
+     * Now we'll spin. And no, we will not put ourselves to sleep
+     * here. This needs to be invoked early on before there even
+     * is such thing as a process context.
+     */
+    while (mu_cpu_aswap(&lock->lock, 1)) {
+        mu_cpu_pause();
+    }
+
+    /* Restore the state if we've mutated it */
+    if (ISSET(flags, SPINLOCK_IRQMUT) && irq_state) {
+        mu_irq_setmask(false);
+    }
+}
+
+void
+spinlock_release(SPINLOCK *lock)
+{
+    if (lock == NULL) {
+        return;
+    }
+
+    mu_cpu_aswap(&lock->lock, 0);
+}