The symptoms of the bug showed up if you were running agetty on ttyS0 but not using ttyS0 as the console= port on the kernel command line. In this case, if you suspended the system you'd get a crash on resume. The specific order of operations that were running: * uart_suspend_port() would be called to put the uart in suspend mode * a tty hangup would be processed * the hangup would call uart_shutdown() * ... suspend / resume happens ... * uart_resume_port() would be called and run the code in the (port->flags & ASYNC_SUSPENDED) block, which would startup the port (and enable tx again). * Since the UART would be available for tx, we'd immediately get an interrupt, eventually calling transmit_chars() * The transmit_chars() function would crash. The first crash would be a dereference of a NULL tty member, but since the port has been shutdown that was just a symptom. Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx> --- drivers/tty/serial/serial_core.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index a3efbea..668e56a 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -255,6 +255,14 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state) } /* + * It's possible for shutdown to be called after suspend. Specifically + * if agetty() is listening to the serial port we get a HUP after the + * suspend happend (and HUP calls shutdown). Clear suspended bit so + * we don't try to resume a port that has been shutdown. + */ + clear_bit(ASYNCB_SUSPENDED, &port->flags); + + /* * kill off our tasklet */ tasklet_kill(&state->tlet); -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
