Date: Sat, 9 Jul 2011 19:42:01 +0200 From: Juergen Lock <nox@jelal.kn-bremen.de> To: freebsd-python@FreeBSD.org Cc: Duncan Findlay <duncan@duncf.ca>, Olivier Cochard-Labbe <olivier@cochard.me>, Benjamin Epitech <mlspirat42@gmail.com> Subject: Re: ports/153167: Problem with signals, threads, and subprocesses in lang/python Message-ID: <20110709174201.GA96487@triton8.kn-bremen.de>
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Hi! (please Cc me with followups, I'm not subscribed)
Has anyone looked at this problem again yet? I found the PR after
debugging the same issue in the emulators/gns3 port, I'm not that
good at python but maybe the workaround I came up with (patch to
gns3's qemuwrapper.py, this is for an updated version of the port
that Olivier is working on) still is useful as a starting point,
maybe something like it could be added to subprocess.py, or
the more portable C equivalent at the appropriate place? (or even
generally in exec*()?)
--- qemuwrapper/qemuwrapper.py.orig
+++ qemuwrapper/qemuwrapper.py
@@ -45,6 +45,7 @@ import SocketServer
import time
import random
import pemubin
+import ctypes
__author__ = 'Thomas Pani and Jeremy Grossmann'
@@ -118,6 +119,33 @@ class xEMUInstance(object):
def unbase_disk(self):
pass
+ def preexec(self):
+ # FreeBSD preexec_fn hack to unblock signals in child processes
+ # to work around the bug in this PR:
+ # http://www.freebsd.org/cgi/query-pr.cgi?pr=ports/153167
+ # inspired by:
+ # http://stackoverflow.com/questions/3791398/how-to-stop-python-from-propagating-signals-to-subprocesses
+
+ # Get the size of the array used to
+ # represent the signal mask
+ SIGSET_NWORDS = 1024 / (8 * ctypes.sizeof(ctypes.c_uint))
+
+ # Define the sigset_t structure
+ class SIGSET(ctypes.Structure):
+ _fields_ = [
+ ('val', ctypes.c_uint * SIGSET_NWORDS)
+ ]
+
+ # Create a new sigset_t to mask out SIGINT
+ sigs = (ctypes.c_uint * SIGSET_NWORDS)()
+ mask = SIGSET(sigs)
+
+ SIG_SETMASK = 3
+ libc = ctypes.CDLL('libc.so')
+
+ # Unblock all signals
+ libc.sigprocmask(SIG_SETMASK, ctypes.pointer(mask), 0)
+
def start(self):
command = self._build_command()
@@ -125,6 +152,7 @@ class xEMUInstance(object):
try:
self.process = subprocess.Popen(command,
stdin=subprocess.PIPE,
+ preexec_fn=self.preexec,
cwd=self.workdir)
except OSError, e:
print >> sys.stderr, "Unable to start instance", self.name, "of", self.__class__
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