From c527fd1f14c27855a37f2e8ac5346ce8d940ced2 Mon Sep 17 00:00:00 2001 From: Tudor Florea Date: Thu, 16 Oct 2014 03:05:19 +0200 Subject: initial commit for Enea Linux 4.0-140929 Migrated from the internal git server on the daisy-enea-point-release branch Signed-off-by: Tudor Florea --- bitbake/lib/bb/daemonize.py | 190 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 190 insertions(+) create mode 100644 bitbake/lib/bb/daemonize.py (limited to 'bitbake/lib/bb/daemonize.py') diff --git a/bitbake/lib/bb/daemonize.py b/bitbake/lib/bb/daemonize.py new file mode 100644 index 0000000000..f0714b3af6 --- /dev/null +++ b/bitbake/lib/bb/daemonize.py @@ -0,0 +1,190 @@ +""" +Python Deamonizing helper + +Configurable daemon behaviors: + + 1.) The current working directory set to the "/" directory. + 2.) The current file creation mode mask set to 0. + 3.) Close all open files (1024). + 4.) Redirect standard I/O streams to "/dev/null". + +A failed call to fork() now raises an exception. + +References: + 1) Advanced Programming in the Unix Environment: W. Richard Stevens + 2) Unix Programming Frequently Asked Questions: + http://www.erlenstar.demon.co.uk/unix/faq_toc.html + +Modified to allow a function to be daemonized and return for +bitbake use by Richard Purdie +""" + +__author__ = "Chad J. Schroeder" +__copyright__ = "Copyright (C) 2005 Chad J. Schroeder" +__version__ = "0.2" + +# Standard Python modules. +import os # Miscellaneous OS interfaces. +import sys # System-specific parameters and functions. + +# Default daemon parameters. +# File mode creation mask of the daemon. +# For BitBake's children, we do want to inherit the parent umask. +UMASK = None + +# Default maximum for the number of available file descriptors. +MAXFD = 1024 + +# The standard I/O file descriptors are redirected to /dev/null by default. +if (hasattr(os, "devnull")): + REDIRECT_TO = os.devnull +else: + REDIRECT_TO = "/dev/null" + +def createDaemon(function, logfile): + """ + Detach a process from the controlling terminal and run it in the + background as a daemon, returning control to the caller. + """ + + try: + # Fork a child process so the parent can exit. This returns control to + # the command-line or shell. It also guarantees that the child will not + # be a process group leader, since the child receives a new process ID + # and inherits the parent's process group ID. This step is required + # to insure that the next call to os.setsid is successful. + pid = os.fork() + except OSError as e: + raise Exception("%s [%d]" % (e.strerror, e.errno)) + + if (pid == 0): # The first child. + # To become the session leader of this new session and the process group + # leader of the new process group, we call os.setsid(). The process is + # also guaranteed not to have a controlling terminal. + os.setsid() + + # Is ignoring SIGHUP necessary? + # + # It's often suggested that the SIGHUP signal should be ignored before + # the second fork to avoid premature termination of the process. The + # reason is that when the first child terminates, all processes, e.g. + # the second child, in the orphaned group will be sent a SIGHUP. + # + # "However, as part of the session management system, there are exactly + # two cases where SIGHUP is sent on the death of a process: + # + # 1) When the process that dies is the session leader of a session that + # is attached to a terminal device, SIGHUP is sent to all processes + # in the foreground process group of that terminal device. + # 2) When the death of a process causes a process group to become + # orphaned, and one or more processes in the orphaned group are + # stopped, then SIGHUP and SIGCONT are sent to all members of the + # orphaned group." [2] + # + # The first case can be ignored since the child is guaranteed not to have + # a controlling terminal. The second case isn't so easy to dismiss. + # The process group is orphaned when the first child terminates and + # POSIX.1 requires that every STOPPED process in an orphaned process + # group be sent a SIGHUP signal followed by a SIGCONT signal. Since the + # second child is not STOPPED though, we can safely forego ignoring the + # SIGHUP signal. In any case, there are no ill-effects if it is ignored. + # + # import signal # Set handlers for asynchronous events. + # signal.signal(signal.SIGHUP, signal.SIG_IGN) + + try: + # Fork a second child and exit immediately to prevent zombies. This + # causes the second child process to be orphaned, making the init + # process responsible for its cleanup. And, since the first child is + # a session leader without a controlling terminal, it's possible for + # it to acquire one by opening a terminal in the future (System V- + # based systems). This second fork guarantees that the child is no + # longer a session leader, preventing the daemon from ever acquiring + # a controlling terminal. + pid = os.fork() # Fork a second child. + except OSError as e: + raise Exception("%s [%d]" % (e.strerror, e.errno)) + + if (pid == 0): # The second child. + # We probably don't want the file mode creation mask inherited from + # the parent, so we give the child complete control over permissions. + if UMASK is not None: + os.umask(UMASK) + else: + # Parent (the first child) of the second child. + os._exit(0) + else: + # 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 + # removed. It's therefore recommended that child branches of a fork() + # and the parent branch(es) of a daemon use _exit(). + return + + # Close all open file descriptors. This prevents the child from keeping + # open any file descriptors inherited from the parent. There is a variety + # of methods to accomplish this task. Three are listed below. + # + # Try the system configuration variable, SC_OPEN_MAX, to obtain the maximum + # number of open file descriptors to close. If it doesn't exists, use + # the default value (configurable). + # + # try: + # maxfd = os.sysconf("SC_OPEN_MAX") + # except (AttributeError, ValueError): + # maxfd = MAXFD + # + # OR + # + # if (os.sysconf_names.has_key("SC_OPEN_MAX")): + # maxfd = os.sysconf("SC_OPEN_MAX") + # else: + # maxfd = MAXFD + # + # OR + # + # Use the getrlimit method to retrieve the maximum file descriptor number + # that can be opened by this process. If there is not limit on the + # resource, use the default value. + # + import resource # Resource usage information. + maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1] + if (maxfd == resource.RLIM_INFINITY): + maxfd = MAXFD + + # Iterate through and close all file descriptors. +# for fd in range(0, maxfd): +# try: +# os.close(fd) +# except OSError: # ERROR, fd wasn't open to begin with (ignored) +# pass + + # Redirect the standard I/O file descriptors to the specified file. Since + # the daemon has no controlling terminal, most daemons redirect stdin, + # stdout, and stderr to /dev/null. This is done to prevent side-effects + # from reads and writes to the standard I/O file descriptors. + + # This call to open is guaranteed to return the lowest file descriptor, + # which will be 0 (stdin), since it was closed above. +# os.open(REDIRECT_TO, os.O_RDWR) # standard input (0) + + # Duplicate standard input to standard output and standard error. +# os.dup2(0, 1) # standard output (1) +# os.dup2(0, 2) # standard error (2) + + + si = file('/dev/null', 'r') + so = file(logfile, 'w') + se = so + + + # Replace those fds with our own + os.dup2(si.fileno(), sys.stdin.fileno()) + os.dup2(so.fileno(), sys.stdout.fileno()) + os.dup2(se.fileno(), sys.stderr.fileno()) + + function() + + os._exit(0) -- cgit v1.2.3-54-g00ecf