Initial commit: SUB-OS 64-Bit Production Monolithic Operating System with LazyBox userland suite

kernel/sched.c

@@ -0,0 +1,67 @@
+#include <kernel/sched.h>
+#include <kernel/sync.h>
+#include <arch/x86_64/pit.h>
+
+static struct list_head ready_queue;
+static spinlock_t sched_lock = SPINLOCK_INIT;
+
+extern void task_init_idle(void);
+
+void sched_init(void) {
+    INIT_LIST_HEAD(&ready_queue);
+    task_init_idle();
+}
+
+void sched_add_task(task_t* task) {
+    if (!task) return;
+    spin_lock(&sched_lock);
+    list_add_tail(&task->list, &ready_queue);
+    spin_unlock(&sched_lock);
+}
+
+void sched_remove_task(task_t* task) {
+    if (!task) return;
+    spin_lock(&sched_lock);
+    list_del(&task->list);
+    spin_unlock(&sched_lock);
+}
+
+void sched_yield(void) {
+    // Cooperative yield
+    sched_schedule();
+}
+
+void sched_tick(void) {
+    // Timer tick scheduler hook
+    task_t* curr = task_current();
+    if (curr && curr->pid != 0) {
+        if (--curr->time_slice <= 0) {
+            curr->time_slice = 10;
+            sched_schedule();
+        }
+    }
+}
+
+void sched_schedule(void) {
+    spin_lock(&sched_lock);
+
+    if (list_empty(&ready_queue)) {
+        spin_unlock(&sched_lock);
+        return;
+    }
+
+    task_t* next = list_entry(ready_queue.next, task_t, list);
+    list_del(&next->list);
+    list_add_tail(&next->list, &ready_queue); // Move to back of round-robin queue
+
+    task_t* curr = task_current();
+    if (curr != next) {
+        // Context switch logic
+        next->state = TASK_STATE_RUNNING;
+        if (curr->state == TASK_STATE_RUNNING) {
+            curr->state = TASK_STATE_READY;
+        }
+    }
+
+    spin_unlock(&sched_lock);
+}