Hi Pavel,

On Thu, Feb 18, 2021 at 02:37:33PM +0100, Pavel Machek wrote:

Close, but see below:

quoted

+static ssize_t ttyname_store(struct device *dev,
+			     struct device_attribute *attr, const char *buf,
+			     size_t size)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	char *ttyname;
+	ssize_t ret = size;
+	bool running;
+
+	if (size > 0 && buf[size - 1] == '\n')
+		size -= 1;
+
+	if (size) {
+		ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
+		if (!ttyname) {
+			ret = -ENOMEM;
+			goto out_unlock;

Unlock without a lock:

quoted

+out_unlock:
+	mutex_unlock(&trigger_data->mutex);

Indeed, I prepare an incremental patch that does return -ENOMEM instead
of goto out_unlock.

quoted

+
+	if (ttyname && !running)
+		ledtrig_tty_restart(trigger_data);
+
+	return ret;
+}

quoted

+
+		tty = tty_kopen_shared(devno);
+		if (IS_ERR(tty) || !tty)
+			/* What to do? retry or abort */
+			goto out;

Abort would make sense to me.

In this case it would IMHO be sensible to already try the
tty_kopen_shared() in ttyname_store() and let that one fail if the tty
doesn't exist. I'll have to go through the history of this patch set, if
I remember correctly it was like that at one point.

quoted

+	if (icount.rx != trigger_data->rx ||
+	    icount.tx != trigger_data->tx) {
+		led_set_brightness(trigger_data->led_cdev, LED_ON);

Please use _sync version.

OK, there are too many variants for me. I'll just believe you that
led_set_brightness_sync is the right one. (Hmm, on the other hand I'll
have to understand the difference for a good commit log. I'll dig into
that. "Pavel said so" probably isn't good enough :-))

Best regards and thanks for your review,
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |