python - Forking a child in another thread: parent doesn't receive SIGCHLD on termination -


normally, when process fork child process, receive sigchld signal if child terminates. but, if fork happens in thread other main thread of application, parent won't receive anything.

i test in python, on different gnu/linux machines. x86_64.

my question is: python behaviour, or defined behaviour of posix standard? , in both cases, why so?

here sample code re-produce behaviour.

import signal import multiprocessing import threading import time   def signal_handler(*args):     print "signal received"  def child_process():     time.sleep(100000)  def child_thread():     p = multiprocessing.process(target=child_process)     p.start()     time.sleep(100000)   signal.signal(signal.sigchld, signal_handler)  p = multiprocessing.process(target=child_process) p.start()  t = threading.thread(target=child_thread) t.start()  time.sleep(100000) print "waked" time.sleep(100000)

then, send sigkill each child. when first child (the 1 forked in main thread) terminates, signal_handler called. when second child terminates, nothing happen.

i test same scenario os.fork instead of multiprocessing.process. same result.

it documented python behavior:

only main thread can set new signal handler, , the main thread 1 receive signals (this enforced python signal module, if underlying thread implementation supports sending signals individual threads). means signals can’t used means of inter-thread communication. use locks instead.


-

Comments

Post a Comment

Popular posts from this blog

scala - 'wrong top statement declaration' when using slick in IntelliJ -

Image
i'm porting project scala 2.9 2.10, therefore have use slick instead of scalaquery. i'm using slick 2.1.0 since supports ms access. according this tutorial , upgrade guide changed robs object class , added val robs : why error message wrong top statement declaration , how rid of it? edit: i'm new scala... according this question seems can't put val outside of methods or classes, right? code above directly in packge. right approach slick then? should move code in class or trait? according this changed val robs = tablequery[robs] to object robs extends tablequery(new robs(_)) {} . no warnings or errors anymore. :)
Read more

c# - DevExpress.Wpf.Grid.InfiniteGridSizeException was unhandled -

Image
when using devexpress, see error: devexpress.wpf.grid.infinitegridsizeexception unhandled message="by default, infinite grid height not allowed since grid rows rendered , hence grid work slowly. fix issue, should place grid container give finite height grid, or should manually specify grid's height or maxheight. note can avoid exception setting gridcontrol.allowinfinitegridsize static property true, in case grid run slowly." the problem dxgrid has infinite height. to fix, set height non-infinite. snoop absolutely invaluable this: if "height" xaml element infinite (i.e. 0 or nan ), can set using one of following: option 1: height="{binding path=actualheight, relativesource={relativesource mode=findancestor, ancestortype=uielement}}" option 2: verticalalignment="stretch" option 3: height="auto" hint: use verticalalignment="stretch" if child of grid <rowdefinition height=
Read more

PySide and Qt Properties: Connecting signals from Python to QML -

i trying run simple pyside appliccation design made in qml. call function in qml python in separated thread. i have following qml view: import qt 4.7 rectangle { visible: true width: 100; height: 100 color: "lightgrey" text { id: datestr objectname: "datestr" x: 10 y: 10 text: "init text" font.pixelsize: 12 function updatedata(text) { datestr.text = qstr(text) console.log("you said: " + text) } } } here application: some imports.... #!/usr/bin/python import sys import time pyside import qtdeclarative, qtcore pyside.qtgui import qapplication pyside.qtdeclarative import qdeclarativeview the qthread worker.... #worker thread class worker(qtcore.qthread): updateprogress = qtcore.signal(int) def __init__(self, child): qtcore.qthread.__init__(self) self.child = child def run(self):
Read more