[PATCH 3 of 4] worker: kill workers after all zombie processes are reaped

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1479384538 -32400
#      Thu Nov 17 21:08:58 2016 +0900
# Node ID 4be342413ddecd0eb6d76c4e5d8bb38fee28061d
# Parent  60c9574e29b43c6d9579b99249ba11ff19af77a0
worker: kill workers after all zombie processes are reaped

Since we now wait child processes in non-blocking way (changed by 7bc25549e084
and e8fb03cfbbde), we don't have to kill them in the middle of the waitpid()
loop. This change will help solving a possible race of waitpid()-pids.discard()
sequence and another SIGCHLD.

waitforworkers() is called by cleanup(), in which case we do killworkers()
beforehand so we can remove killworkers() from waitforworkers().

diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -119,9 +119,10 @@ def _posixworker(ui, func, staticargs, a
                 st = _exitstatus(st)
             if st and not problem[0]:
                 problem[0] = st
-                killworkers()
     def sigchldhandler(signum, frame):
         waitforworkers(blocking=False)
+        if problem[0]:
+            killworkers()
     oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler)
     for pargs in partition(args, workers):
         pid = os.fork()