Add bitbake-dev to allow ease of testing and development of bitbake trunk

git-svn-id: https://svn.o-hand.com/repos/poky/trunk@5337 311d38ba-8fff-0310-9ca6-ca027cbcb966

bitbake-dev/lib/bb/daemonize.py

@@ -0,0 +1,189 @@
+"""
+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.
+UMASK = 0
+
+# 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, 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, 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.
+         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)
+