Device testing has various problems:
- the main thread doesn't halt the serial monitoring thread when an
error occurs while flashing, meaning flash errors can look like
timeouts
- serial_line is unbound if the ser.readline() call raises an
exception, so the following "if serial_line" would raise NameError
in that case
- the serial monitoring thread is not a daemon, so exceptions or
errors in the handle() thread that cause thread exit will leave the
process sitting around until the serial monitoring thread has a
chance to exit
Fix these issues:
- Rewrite the serial monitoring thread as a select loop over the
serial port file descriptor and a pipe shared by the main thread and
serial monitoring thread. If flashing fails, the main thread uses
the pipe to signal to the serial monitoring thread that it should
exit.
- Make sure serial_line is always bound when read.
- Mark the serial thread daemonic.
Signed-off-by: Marti Bolivar <marti@foundries.io>
5591ca2374