test/recv-mshot-fair: submit !DEFER receives at the same time

The test currently allows !DEFER to be unfair after resubmission,
because it would arm each recv as needed and submit it at the same time.
This means that once they are all done, R1 will be submitted separately
and process the remaining, and repeat for R2..R4. That causes
unfairness, as only one recv would be pending at the time for that case.

Keep track of pending submits and do them in one go, preserving fairness
even for !DEFER.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

test/recv-mshot-fair.c

@@ -155,7 +155,7 @@ static int recv_get_cqe(struct io_uring *ring,
 	int ret;
 
 	do {
-		ret = io_uring_submit_and_wait_timeout(ring, cqe, 1, &ts, NULL);
+		ret = io_uring_wait_cqe_timeout(ring, cqe, &ts);
 		if (!ret) {
 			struct recv_data *rd = io_uring_cqe_get_data(*cqe);
 
@@ -196,6 +196,7 @@ static int do_recv(struct io_uring *ring)
 	struct recv_data *rd;
 	int ret = 1;
 	int done = 0;
+	int pending_submit = 0;
 
 	last_rd = NULL;
 	bytes_since_last = 0;
@@ -224,8 +225,12 @@ static int do_recv(struct io_uring *ring)
 			continue;
 		}
 		io_uring_cqe_seen(ring, cqe);
-		if (!(cqe->flags & IORING_CQE_F_MORE) && rd->recv_bytes)
+		if (!(cqe->flags & IORING_CQE_F_MORE) && rd->recv_bytes) {
 			arm_recv(ring, rd);
+			pending_submit++;
+		}
+		if (pending_submit == NR_RDS)
+			io_uring_submit(ring);
 	} while (done < NR_RDS);
 
 	ret = 0;
@@ -455,7 +460,6 @@ static int run_tests(void)
 		return T_EXIT_FAIL;
 	}
 
-	/* DEFER_TASKRUN should be fully fair and not have overshoots */
 	if (r.unfair || r.mshot_too_big) {
 		fprintf(stderr, "DEFER unfair=%d, too_big=%d\n", r.unfair, r.mshot_too_big);
 		return T_EXIT_FAIL;
@@ -467,13 +471,7 @@ static int run_tests(void)
 		return T_EXIT_FAIL;
 	}
 
-	/*
-	 * normal task_work should not have overshoots, but may not be fair
-	 * because of the re-arming.
-	 */
-	if (r.unfair)
-		fprintf(stdout, "!DEFER bundle unfair, expected\n");
-	if (r.mshot_too_big) {
+	if (r.unfair || r.mshot_too_big) {
 		fprintf(stderr, "!DEFER bundle too_big=%d\n", r.mshot_too_big);
 		return T_EXIT_FAIL;
 	}
@@ -484,13 +482,7 @@ static int run_tests(void)
 		return T_EXIT_FAIL;
 	}
 
-	/*
-	 * normal task_work should not have overshoots, but may not be fair
-	 * because of the re-arming.
-	 */
-	if (r.unfair)
-		fprintf(stdout, "!DEFER unfair, expected\n");
-	if (r.mshot_too_big) {
+	if (r.unfair || r.mshot_too_big) {
 		fprintf(stderr, "!DEFER too_big=%d\n", r.mshot_too_big);
 		return T_EXIT_FAIL;
 	}