From fcc8e1ff53696f78dd64b4ee32f3c433b7a47df0 Mon Sep 17 00:00:00 2001 From: Joshua Watt Date: Tue, 21 Aug 2018 09:04:16 -0500 Subject: daemonize: Flush stdio on exit In spite of a comment suggesting otherwise, os._exit() does not flush buffered output from file descriptors before exiting the process like os.exit() does. This means that any un-flushed output is lost in the daemon process, in particular the traceback from any thrown exceptions, making debugging exceptions in the daemon quite difficult. The solution is to flush stdout and stderr before exiting. Signed-off-by: Joshua Watt Signed-off-by: Richard Purdie --- lib/bb/daemonize.py | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/lib/bb/daemonize.py b/lib/bb/daemonize.py index 8300d1d0f..bf1679346 100644 --- a/lib/bb/daemonize.py +++ b/lib/bb/daemonize.py @@ -49,8 +49,8 @@ def createDaemon(function, logfile): # exit() or _exit()? # _exit is like exit(), but it doesn't call any functions registered # with atexit (and on_exit) or any registered signal handlers. It also - # closes any open file descriptors. Using exit() may cause all stdio - # streams to be flushed twice and any temporary files may be unexpectedly + # closes any open file descriptors, but doesn't flush any buffered output. + # Using exit() may cause all any temporary files to be unexpectedly # removed. It's therefore recommended that child branches of a fork() # and the parent branch(es) of a daemon use _exit(). os._exit(0) @@ -79,4 +79,9 @@ def createDaemon(function, logfile): traceback.print_exc() finally: bb.event.print_ui_queue() + # os._exit() doesn't flush open files like os.exit() does. Manually flush + # stdout and stderr so that any logging output will be seen, particularly + # exception tracebacks. + sys.stdout.flush() + sys.stderr.flush() os._exit(0) -- cgit 1.2.3-korg