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USB: serial: metro-usb: fix unthrottle race

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If the completion handler races with unthrottle() both functions may try
to resubmit the same interrupt-in urb, but at most one will succeed.

Fix the unthrottle logic using a throttle-requested flag so that only
one attempt to resubmit the urb is made to avoid logging an error.

Fixes: 43d186fe99 ("USB: serial: add metro-usb driver to the tree")
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2026-06-23 17:21:47 +02:00
parent c41d491929
commit 563cd5aacd
1 changed files with 17 additions and 8 deletions
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25
drivers/usb/serial/metro-usb.c
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@ -36,6 +36,7 @@
struct metrousb_private {
spinlock_t lock;
int throttled;
int throttle_req;
unsigned long control_state;
};
@ -143,7 +144,10 @@ static void metrousb_read_int_callback(struct urb *urb)
/* Set any port variables. */
spin_lock_irqsave(&metro_priv->lock, flags);
throttled = metro_priv->throttled;
if (metro_priv->throttle_req) {
metro_priv->throttled = 1;
throttled = 1;
}
spin_unlock_irqrestore(&metro_priv->lock, flags);
if (throttled)
@ -175,6 +179,7 @@ static int metrousb_open(struct tty_struct *tty, struct usb_serial_port *port)
spin_lock_irqsave(&metro_priv->lock, flags);
metro_priv->control_state = 0;
metro_priv->throttled = 0;
metro_priv->throttle_req = 0;
spin_unlock_irqrestore(&metro_priv->lock, flags);
/* Clear the urb pipe. */
@ -269,7 +274,7 @@ static void metrousb_throttle(struct tty_struct *tty)
/* Set the private information for the port to stop reading data. */
spin_lock_irqsave(&metro_priv->lock, flags);
metro_priv->throttled = 1;
metro_priv->throttle_req = 1;
spin_unlock_irqrestore(&metro_priv->lock, flags);
}
@ -321,19 +326,23 @@ static void metrousb_unthrottle(struct tty_struct *tty)
struct usb_serial_port *port = tty->driver_data;
struct metrousb_private *metro_priv = usb_get_serial_port_data(port);
unsigned long flags;
int throttled;
int result = 0;
/* Set the private information for the port to resume reading data. */
spin_lock_irqsave(&metro_priv->lock, flags);
throttled = metro_priv->throttled;
metro_priv->throttled = 0;
metro_priv->throttle_req = 0;
spin_unlock_irqrestore(&metro_priv->lock, flags);
/* Submit the urb to read from the port. */
result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
if (result)
dev_err(&port->dev,
"failed submitting interrupt in urb error code=%d\n",
result);
if (throttled) {
result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
if (result) {
dev_err(&port->dev, "failed to submit interrupt in urb: %d\n",
result);
}
}
}
static struct usb_serial_driver metrousb_device = {