Re: Race condition in TTY ldisc layer in 2.6.33

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, 11 Mar 2010, [iso-8859-2] Micha³ Miros³aw wrote:

> On Thu, Mar 11, 2010 at 04:50:15PM +0100, Micha³ Miros³aw wrote:
> > On Thu, Mar 11, 2010 at 05:50:09AM -0800, Greg KH wrote:
> > > On Thu, Mar 11, 2010 at 02:32:22PM +0100, Micha? Miros?aw wrote:
> > > > Looks like there's some race contition in switching ldiscs on USB serial
> > > > ports. The following warnings trigger sometimes after killing and restarting
> > > > process that changes ldisc and waits forever. In case you want to look at
> > > > the code, there it is: http://rere.qmqm.pl/~mirq/sermmc/
> > > If you apply git commit 638b9648ab51c9c549ff5735d3de519ef6199df3 to the
> > > 2.6.33 kernel, does it solve the issue for you?
> > I'm running with the patch now. After couple cycles of starting and killing
> > the ldisc-setting process I get no warnings. I'll get back to you when/if
> > I encounter them again.
> 
> Hah. Just seconds after I sent that mail I hit this again. The stack traces
> are exactly the same (except for different starting address of
> flush_to_ldisc()).
> 
> The warnings are triggered by:
> 
> 	struct usb_serial_port *port = tty->driver_data;
> 	...
> 	/* count is managed under the mutex lock for the tty so cannot
> 	   drop to zero until after the last close completes */
> 	WARN_ON(!port->port.count);
> 
> BTW, Couple of minutes earlier I got this message:
> 
> [  201.629616] cp210x ttyUSB0: usb_serial_generic_resubmit_read_urb - failed resubmitting read urb, error -1
> 
> But after that I disconnected and reconnected the device, so this is probably
> not relevant here.

It looks like Greg gave you the wrong commit ID.  You should use this
one: 49d3380e3f1297ff7bdc700c0a7fe6c3a036b3ab.  It removes those
WARN_ON statements entirely.

Actually, you should use both commits.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux