netdev - Re: [RFC] Patch to option HSO driver to the kernel

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Date:	Tue, 15 Apr 2008 15:06:19 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Greg KH <greg@...ah.com>
Cc:	linux-usb@...r.kernel.org, netdev@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Filip Aben <f.aben@...ion.com>,
	Paulius Zaleckas <paulius.zaleckas@...tonika.lt>,
	ajb@...eresystems.co.uk
Subject: Re: [RFC] Patch to option HSO driver to the kernel

Am Montag, 14. April 2008 23:32:39 schrieb Greg KH:
> Hi all,
> 
> Here's a patch that I have cleaned up for context only from Option that
> is a USB serial / network device all in one.
> 
> I'd like to see this go into 2.6.26, so any review comments by anyone
> who wishes to review any portion of this would be greatly apprecited.

This incremental patch fixes a race where write can mess with
an URB while it isn't yet returned.

	Regards
		Oliver

Signed-off-by: Oliver Neukum <oneukum@...e.de>

---

--- linux-2.6.25-rc7-work/drivers/net/usb/hso.c.alt	2008-04-15 13:59:21.000000000 +0200
+++ linux-2.6.25-rc7-work/drivers/net/usb/hso.c	2008-04-15 14:44:45.000000000 +0200
@@ -220,6 +220,7 @@ struct hso_serial {
 	unsigned long flags;
 	u8 rts_state;
 	u8 dtr_state;
+	int tx_urb_used:1;
 
 	/* from usb_serial_port */
 	struct tty_struct *tty;
@@ -1521,12 +1522,13 @@ static void hso_kick_transmit(struct hso
 {
 	u8 *temp = NULL;
 	unsigned long flags;
+	int res;
 
 	spin_lock_irqsave(&serial->serial_lock, flags);
 	if (!serial->tx_buffer_count)
 		goto out;
 
-	if (serial->tx_urb->status == -EINPROGRESS)
+	if (serial->tx_urb_used)
 		goto out;
 
 	/* Wakeup USB interface if necessary */
@@ -1540,10 +1542,13 @@ static void hso_kick_transmit(struct hso
 	serial->tx_data_count = serial->tx_buffer_count;
 	serial->tx_buffer_count = 0;
 
-out:
 	/* If temp is set, it means we switched buffers */
-	if (temp && serial->write_data)
-		serial->write_data(serial);
+	if (temp && serial->write_data) {
+		res = serial->write_data(serial);
+		if (res >= 0)
+			serial->tx_urb_used = 1;
+	}
+out:
 	spin_unlock_irqrestore(&serial->serial_lock, flags);
 }
 
@@ -1783,6 +1788,9 @@ static void ctrl_callback(struct urb *ur
 	if (!serial)
 		return;
 
+	spin_lock(&serial->serial_lock);
+	serial->tx_urb_used = 0;
+	spin_unlock(&serial->serial_lock);
 	if (status) {
 		log_usb_status(status, __func__);
 		return;
@@ -1914,6 +1922,9 @@ static void hso_std_serial_write_bulk_ca
 		return;
 	}
 
+	spin_lock(&serial->serial_lock);
+	serial->tx_urb_used = 0;
+	spin_unlock(&serial->serial_lock);
 	if (status) {
 		log_usb_status(status, __func__);
 		return;
--
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