sched: enforce ref-counting on current task/thread pointers

vm/address-space.c

@@ -1261,9 +1261,11 @@ static kern_status_t request_missing_page(
 	/* here:
 	 * `region` is locked.
 	 * `object` is unlocked.
-	 * `irq_flags` must be restored when `region` is unlocked.
-	 * the relevant page in `object` may or may not be committed.
-	 * if it isn't, it needs to be requested.
+	 * `irq_flags` must be restored when `region` is
+	 * unlocked.
+	 * the relevant page in `object` may or may
+	 * not be committed. if it isn't, it needs to be
+	 * requested.
 	 */
 	vm_object_lock(object);
 	address_space_unlock(region);

vm/vm-controller.c

@@ -159,6 +159,7 @@ kern_status_t vm_controller_recv(
 	spin_unlock(&req->req_lock);
 
 	if (req->req_status == PAGE_REQUEST_ASYNC) {
+		put_current_thread(req->req_sender);
 		vm_cache_free(&page_request_cache, req);
 	}
 
@@ -220,7 +221,7 @@ kern_status_t vm_controller_detach_object(
 	req->req_type = PAGE_REQUEST_DETACH;
 	req->req_status = PAGE_REQUEST_ASYNC;
 	req->req_object = vmo->vo_key;
-	req->req_sender = current_thread();
+	req->req_sender = get_current_thread();
 	send_request_async(ctrl, req);
 
 	vmo->vo_ctrl = NULL;
@@ -236,7 +237,7 @@ static void wait_for_reply(
 	unsigned long *lock_flags)
 {
 	struct wait_item waiter;
-	struct thread *self = current_thread();
+	struct thread *self = get_current_thread();
 
 	wait_item_init(&waiter, self);
 	for (;;) {
@@ -251,6 +252,7 @@ static void wait_for_reply(
 	}
 
 	self->tr_state = THREAD_READY;
+	put_current_thread(self);
 }
 
 static void fulfill_requests(

vm/vm-object.c

@@ -376,7 +376,7 @@ static kern_status_t request_page(
 	req.req_type = PAGE_REQUEST_READ;
 	req.req_offset = offset;
 	req.req_length = vm_page_order_to_bytes(VM_PAGE_4K);
-	req.req_sender = current_thread();
+	req.req_sender = get_current_thread();
 
 	object_ref(&vo->vo_base);
 	req.req_object = vo->vo_key;
@@ -388,6 +388,7 @@ static kern_status_t request_page(
 	kern_status_t status
 		= vm_controller_send_request(ctrl, &req, irq_flags);
 
+	put_current_thread(req.req_sender);
 	spin_unlock(&req.req_lock);
 	vm_controller_unlock_irqrestore(ctrl, *irq_flags);
 	object_unref(&vo->vo_base);