From 0894b8f5c0b18b7fbbfe505bf8291495c74a3f08 Mon Sep 17 00:00:00 2001
From: David Härdeman <david@hardeman.nu>
Date: Fri, 12 Jun 2020 00:52:39 +0200
Subject: Improve tagged pointer handling

---
 uring.c | 93 +++++++++++++++++++++++++++++++++++++----------------------------
 1 file changed, 53 insertions(+), 40 deletions(-)

(limited to 'uring.c')

diff --git a/uring.c b/uring.c
index 9075327..4c524c7 100644
--- a/uring.c
+++ b/uring.c
@@ -16,6 +16,15 @@ struct uring_ev {
 	struct uring_task task;
 };
 
+enum cqe_type {
+	CQE_TYPE_NORMAL		= 0x0,
+	CQE_TYPE_CANCEL		= 0x1,
+	CQE_TYPE_CLOSE		= 0x2,
+	CQE_TYPE_POLL_CANCEL	= 0x3
+};
+
+#define CQE_TYPE_PTR_MASK 0x3
+
 uint64_t sqe_count = 0;
 uint64_t cqe_count = 0;
 
@@ -92,7 +101,7 @@ uring_task_destroy(struct cfg *cfg, struct uring_task *task)
 	
 		sqe = get_sqe(cfg, task);
 		io_uring_prep_cancel(sqe, task, 0);
-		io_uring_sqe_set_data(sqe, (void *)((uintptr_t)task + 0x1));
+		io_uring_sqe_set_data(sqe, (void *)((uintptr_t)task | CQE_TYPE_CANCEL));
 	}
 
 	task->dead = true;
@@ -228,9 +237,8 @@ uring_close(struct cfg *cfg, struct uring_task *task, int fd)
 	}
 
        	sqe = get_sqe(cfg, task);
-	task = (void *)((uintptr_t)task + 0x2);
 	io_uring_prep_close(sqe, fd);
-	io_uring_sqe_set_data(sqe, task);
+	io_uring_sqe_set_data(sqe, (void *)((uintptr_t)task | CQE_TYPE_CLOSE));
 }
 
 static void
@@ -483,8 +491,7 @@ uring_poll_cancel(struct cfg *cfg, struct uring_task *task)
 	sqe = get_sqe(cfg, task);
 	task->dead = true;
 	io_uring_prep_poll_remove(sqe, task);
-	/* FIXME: should not set this to NULL */
-	io_uring_sqe_set_data(sqe, NULL);
+	io_uring_sqe_set_data(sqe, (void *)((uintptr_t)task | CQE_TYPE_POLL_CANCEL));
 }
 
 static void
@@ -530,6 +537,21 @@ uring_init(struct cfg *cfg)
 	uev->cfg = cfg;
 }
 
+static inline void
+uring_print_cqe(struct cfg *cfg, const char *type, struct uring_task *task,
+		struct io_uring_cqe *cqe)
+{
+	fprintf(stderr, "uring_event_loop: got %s CQE "
+		"(res: %i (%s), task: %s (%p), fd: %i, cb: %p)\n",
+		type,
+		cqe->res,
+		cqe->res < 0 ? strerror(-cqe->res) : "ok",
+		task->name ? task->name : "<none>",
+		task,
+		task->fd,
+		task->callback);
+}
+
 void
 uring_event_loop(struct cfg *cfg)
 {
@@ -551,54 +573,45 @@ uring_event_loop(struct cfg *cfg)
 		io_uring_for_each_cqe(&cfg->uev->uring, head, cqe) {
 			struct uring_task *task = io_uring_cqe_get_data(cqe);
 			bool do_callback;
+			enum cqe_type cqe_type;
 
 			cqe_count++;
 
+			cqe_type = ((uintptr_t)task & CQE_TYPE_PTR_MASK);
+			task = (void *)((uintptr_t)task & ~CQE_TYPE_PTR_MASK);
+
 			if (!task)
 				die("%s: null task\n", __func__);
 
-			if (task != NULL && ((uintptr_t)task & 0x1)) {
-				task = (void *)((uintptr_t)task - 0x1);
-				fprintf(stderr, "%s: got cancellation CQE (res: %i (%s), task: %s (%p), fd: %i, cb: %p)\n",
-					__func__,
-					cqe->res,
-					cqe->res < 0 ? strerror(-cqe->res) : "ok",
-					task ? task->name : "<none>",
-					task,
-					task ? task->fd : -1,
-					task ? task->callback : NULL);
+			switch (cqe_type) {
+			case CQE_TYPE_CANCEL:
+				uring_print_cqe(cfg, "cancel", task, cqe);
 				do_callback = false;
-			} else if (task != NULL && ((uintptr_t)task & 0x2)) {
-				task = (void *)((uintptr_t)task - 0x2);
-				fprintf(stderr, "%s: got close CQE (res: %i (%s), task: %s (%p), fd: %i, cb: %p)\n",
-					__func__,
-					cqe->res,
-					cqe->res < 0 ? strerror(-cqe->res) : "ok",
-					task ? task->name : "<none>",
-					task,
-					task ? task->fd : -1,
-					task ? task->callback : NULL);
+				break;
+
+			case CQE_TYPE_CLOSE:
+				uring_print_cqe(cfg, "close", task, cqe);
+				do_callback = false;
+				break;
+
+			case CQE_TYPE_POLL_CANCEL:
+				uring_print_cqe(cfg, "poll_cancel", task, cqe);
 				do_callback = false;
-			} else {
-				fprintf(stderr, "%s: got CQE (res: %i (%s), task: %s (%p), fd: %i, cb: %p)\n",
-					__func__,
-					cqe->res,
-					cqe->res < 0 ? strerror(-cqe->res) : "ok",
-					task ? task->name : "<none>",
-					task,
-					task ? task->fd : -1,
-					task ? task->callback : NULL);
+				break;
+
+			case CQE_TYPE_NORMAL:
+				uring_print_cqe(cfg, "standard", task, cqe);
 				do_callback = true;
-			}
+				break;
 
-			if (!task)
-				error("%s: null task!?\n", __func__);
+			default:
+				die("%s: unknown CQE type\n");
+			}
 
-			if (do_callback && task && task->callback)
+			if (do_callback && task->callback)
 				task->callback(cfg, task, cqe->res);
 
-			if (task)
-				uring_task_put(cfg, task);
+			uring_task_put(cfg, task);
 
 			if (exiting)
 				return;
-- 
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