On Wed, Aug 20, 2025 at 10:37:01PM +0200, Andrew Lunn wrote:

quoted

+static int mucse_mbx_fw_post_req(struct mucse_hw *hw,
+				 struct mbx_fw_cmd_req *req,
+				 struct mbx_req_cookie *cookie)
+{
+	int len = le16_to_cpu(req->datalen);
+	int err;
+
+	cookie->errcode = 0;
+	cookie->done = 0;
+	init_waitqueue_head(&cookie->wait);
+	err = mutex_lock_interruptible(&hw->mbx.lock);
+	if (err)
+		return err;
+	err = mucse_write_mbx(hw, (u32 *)req, len);
+	if (err)
+		goto out;
+	err = wait_event_timeout(cookie->wait,
+				 cookie->done == 1,
+				 cookie->timeout_jiffies);
+
+	if (!err)
+		err = -ETIMEDOUT;
+	else
+		err = 0;
+	if (!err && cookie->errcode)
+		err = cookie->errcode;
+out:
+	mutex_unlock(&hw->mbx.lock);
+	return err;

What is your design with respect to mutex_lock_interruptible() and
then calling wait_event_timeout() which will ignore signals?

Is your intention that you can always ^C the driver, and it will clean
up whatever it was doing and return -EINTR? Such unwinding can be
tricky and needs careful review. Before i do that, i just want to make
sure this is your intention, and you yourself have carefully reviewed
the code.

   Andrew

'mucse_mbx_fw_post_req' is designed can be called by 'cat /sys/xxx', So I used
xx_interruptible() before.
The design sequence is:
write_mbx with cookie ------> fw ----> dirver_irq_handler(call wake_up)
			|                |
			V                V
	   wait_event_xxxx  ------------------->  free(cookie)

But if ^C just after 'wait_event_interruptible_timeout', cookie will
be free before fw really response, a crash will happen.
cookie pointer is in mbx.req, and fw response with no change.

write_mbx with cookie ------> fw ---------> dirver_irq_handler(call wake_up)
			|                          |
			V                          V
	   wait_event_xxxx  --->  free(cookie)   crash with freed cookie
			     |
			     v
			    ^C

So I use goto retry if -ERESTARTSYS with wait_event_interruptible_timeout.
And it is the same with wait_event_timeout.
If ^C in mutex_lock_interruptible, it is safe return since no write to
fw and no response from fw.