lib: add generic resource allocator

kernel-src/lib/resource_allocator.c

@@ -0,0 +1,62 @@
+#include <resource_allocator.h>
+#include <arch/cpu.h>
+
+static void insert(resource_allocator_t *allocator, resource_allocator_waiter_t *node) {
+	if (allocator->queue) {
+		allocator->tail->next = node;
+		allocator->tail = node;
+	} else {
+		allocator->queue = node;
+		allocator->tail = node;
+	}
+}
+
+static void pop(resource_allocator_t *allocator) {
+	resource_allocator_waiter_t *w = allocator->queue;
+	allocator->queue = w->next;
+	sched_wakeup(w->thread, 0);
+}
+
+void resource_allocator_init(resource_allocator_t *allocator, size_t resource_total, size_t allocate_max) {
+	MUTEX_INIT(&allocator->mutex);
+	allocator->queue = allocator->tail = NULL;
+	allocator->resource_current = resource_total;
+	allocator->allocate_max = allocate_max;
+}
+
+void resource_allocate(resource_allocator_t *allocator, size_t count) {
+	MUTEX_ACQUIRE(&allocator->mutex);
+
+	if (allocator->queue || allocator->resource_current < count) {
+		resource_allocator_waiter_t waiter = {
+			.requested = count,
+			.thread = current_thread(),
+			.next = NULL
+		};
+
+		insert(allocator, &waiter);
+		sched_prepare_sleep(false);
+		MUTEX_RELEASE(&allocator->mutex);
+		sched_yield();
+		return;
+	}
+
+	allocator->resource_current -= count;
+	
+	MUTEX_RELEASE(&allocator->mutex);
+}
+
+void resource_free(resource_allocator_t *allocator, size_t count) {
+	count = min(allocator->allocate_max, count);
+	MUTEX_ACQUIRE(&allocator->mutex);
+
+	allocator->resource_current += count;
+
+	while (allocator->queue && allocator->queue->requested <= allocator->resource_current) {
+		allocator->resource_current -= allocator->queue->requested;
+
+		pop(allocator);
+	}
+	
+	MUTEX_RELEASE(&allocator->mutex);
+}