auto-test: Add test for blocking write case

This testcase writes out lots of stuff to the host without reading
anything out on the host.  The guest should just go wait while the host
clears out all the buffers.  (Some badness caused the whole guest to
freeze in this case, but a patch that should make it to stable kernels
do just what's required.)

This testcase is very similar to the nonblocking write testcase, as they
check similar things.

Signed-off-by: Amit Shah <amit.shah@redhat.com>

1 files changed, 61 insertions, 1 deletions

diff --git a/auto-virtserial.c b/auto-virtserial.c
index 4b346f6..df0efd6 100644
--- a/auto-virtserial.c
+++ b/auto-virtserial.c
@@ -568,9 +568,69 @@ out:
 	return err;
 }
 
+/*
+ * Similar to test_nonblocking_write(): open guest port, write
+ * lots of data.  We should be put to sleep once the host
+ * can't accept any more data.  Then read some data from host,
+ * we should be writable again.
+ */
 static int test_blocking_write(int nr)
 {
-	return 0;
+	void *buf;
+	unsigned int i;
+	int err, ret;
+
+	ret = guest_open_port(nr);
+	err = result(__func__, true, "guest open", ret, -1, -1, OP_GT, false);
+	if (err)
+		return err;
+
+	host_connect_chardev(nr);
+
+	/*
+	 * We currently have 128 buffers in a virtqueue --
+	 * hw/virtio-serial-bus.c, so this while loop should stop when
+	 * i is 128.  However, the loop actually stops when i is 158
+	 * -- the qemu chardev itself can buffer some data.
+	 */
+	for (i = 0; i < 200; i++) {
+		ret = guest_poll(nr, 0, 0);
+		if (i && ret == 0) {
+			/* vq full.  Next write will block. */
+			break;
+		}
+		err = result(__func__, true, "guest poll", ret,
+			     POLLOUT, POLLOUT, OP_EQ, false);
+		if (err)
+			goto out;
+
+		ret = guest_write(nr, BUF_LENGTH);
+		err = result(__func__, true, "guest write",
+			     ret, BUF_LENGTH, BUF_LENGTH, OP_EQ, false);
+		if (err)
+			goto out;
+	}
+
+	buf = malloc(BUF_LENGTH);
+	for (i = 0; i < 32; i++) {
+		/*
+		 * One last thing: read out some buffers from host
+		 * (more than the qemu-chardev buffer limit).  See if
+		 * guest gets POLLOUT set.
+		 */
+		read(chardevs[nr].sock, buf, BUF_LENGTH);
+	}
+	free(buf);
+
+	sleep(2);
+
+	ret = guest_poll(nr, 0, 0);
+	err = result(__func__, true, "read-poll",
+		     ret, POLLOUT, POLLOUT, OP_EQ, true);
+out:
+	host_close_chardev(nr);
+	guest_close_port(nr);
+	return err;
 }
 
 static int test_nonblocking_write(int nr)