On Sun, Apr 14, 2013 at 10:35:28PM +0100, Bryan O'Donoghue wrote: > Greetings. > > I'm working with an x86 system connected to a RTU via a 232 port. > > A simple test we run nightly - opens and closes this serial port - > sending some simple commands to a daemon monitoring the serial line. > > After up-version from 3.5.x to 3.8.y-stable we found regular lockups > of the serial port. > > This was root caused to the waggling of the DCD signal on the serial line. > > This results in getty => login => /bin/bash as showing in the "DW" > state (hung) - forever, when interrogated with "ps". In other words > after logging in via the serial port and closing a kermit/minicom > session - where the DCD line happens to be de-asserted to the target > box, the login task gets indefinitely hung. > > do_tty_hangup() is being called by uart_handle_dcd_change() which > triggers the bug and locks the task and consequently never releases > the serial port. > > Switching on mutex debugging - shows the printout below. > > Both the hung task and the mutex debug trace go away once > 852e4a8152b427c3f318bb0e1b5e938d64dcdc32 by Sebastian Andrzej > Siewior is applied from upstream. > > Suggest application to stable, ASAP. Now applied, thanks for testing and letting us know to backport this. greg k-h -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html