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
