# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1479383045 -32400
# Node ID 237b2883cbd86478c3b073de0e3dbee7ebdf7239
# Parent  0e6ce6313e4739db4793a231e76be03e83cc246d
worker: make sure killworkers() never be interrupted by another SIGCHLD

killworkers() iterates over pids, which can be updated by SIGCHLD handler.
So we should either copy pids or prevent killworkers() from being interrupted
by SIGCHLD. I chose the latter as it is simpler and can make pids handling
more consistent.

This fixes a possible "set changed size during iteration" error at
killworkers() before cleanup().

diff -r 0e6ce6313e47 -r 237b2883cbd8 mercurial/worker.py
--- a/mercurial/worker.py	Thu Nov 17 21:43:01 2016 +0900
+++ b/mercurial/worker.py	Thu Nov 17 20:44:05 2016 +0900
@@ -89,6 +89,10 @@
     signal.signal(signal.SIGINT, signal.SIG_IGN)
     pids, problem = set(), [0]
     def killworkers():
+        # unregister SIGCHLD handler as all children will be killed. This
+        # function shouldn't be interrupted by another SIGCHLD; otherwise pids
+        # could be updated while iterating, which would cause inconsistency.
+        signal.signal(signal.SIGCHLD, oldchldhandler)
         # if one worker bails, there's no good reason to wait for the rest
         for p in pids:
             try:
@@ -115,8 +119,6 @@
                 st = _exitstatus(st)
             if st and not problem[0]:
                 problem[0] = st
-                # unregister SIGCHLD handler as all children will be killed
-                signal.signal(signal.SIGCHLD, oldchldhandler)
                 killworkers()
     def sigchldhandler(signum, frame):
         waitforworkers(blocking=False)