# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 2015-10-08 17:57:03
# Node ID c0501c26b05c6f50b8638753306dfc13144fe5d6
# Parent  f18646cf0e936287237160f33289f065cf02eb7b

worker: restore old countcpus code (issue4869)

This is a backout of d29859cfcfc2. The stdlib implementation of
multiprocessing.cpu_count() attempts to invoke a process on BSD and
Darwin platforms (at least on 2.7). Under certain conditions (such as
cwd being removed) this could raise. Our old code was silently catching
the exception.

The old code was more robust, so restore it.

diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -8,7 +8,6 @@
 from __future__ import absolute_import
 
 import errno
-import multiprocessing
 import os
 import signal
 import sys
@@ -19,10 +18,24 @@ from . import util
 
 def countcpus():
     '''try to count the number of CPUs on the system'''
+
+    # posix
     try:
-        return multiprocessing.cpu_count()
-    except NotImplementedError:
-        return 1
+        n = int(os.sysconf('SC_NPROCESSORS_ONLN'))
+        if n > 0:
+            return n
+    except (AttributeError, ValueError):
+        pass
+
+    # windows
+    try:
+        n = int(os.environ['NUMBER_OF_PROCESSORS'])
+        if n > 0:
+            return n
+    except (KeyError, ValueError):
+        pass
+
+    return 1
 
 def _numworkers(ui):
     s = ui.config('worker', 'numcpus')