[PATCH 8 of 8 V5] worker: stop using a separate thread waiting for children

[Martin von Zweigbergk]

On Mon, Nov 14, 2016 at 6:39 PM, Jun Wu <quark at fb.com> wrote:
> # HG changeset patch
> # User Jun Wu <quark at fb.com>
> # Date 1478919967 0
> #      Sat Nov 12 03:06:07 2016 +0000
> # Node ID 977775ff43115c001579973ef09581f102b1b842
> # Parent  3a463b68088ed4721b0b0a33504143b7eff65ade
> # Available At https://bitbucket.org/quark-zju/hg-draft
> #              hg pull https://bitbucket.org/quark-zju/hg-draft -r 977775ff4311
> worker: stop using a separate thread waiting for children

Just to make sure you didn't miss 9955fc5ee24b (worker: handle worker
failures more aggressively, 2013-02-20), which has this in the
message:

"We now wait for worker processes in a separate thread, so that we can
spot failures in a timely way, wihout waiting for the progress pipe
to drain."

I haven't followed the discussion on this series, so I'm sorry if this
has already been brought up. I also don't know much about how
worker.py works, I just happened to see that commit message and
thought it sounded like you're undoing that and wanted to make sure
you had seen that commit. I have no opinion about it myself; if you
tell me it's not an issue, I will happily take your word for it.


>
> Now that we have a SIGCHLD hander, and it could get executed when waiting
> for I/O. It's no longer necessary to have a separated waitpid thread. So
> just remove it.
>
> diff --git a/mercurial/worker.py b/mercurial/worker.py
> --- a/mercurial/worker.py
> +++ b/mercurial/worker.py
> @@ -13,5 +13,4 @@ import os
>  import signal
>  import sys
> -import threading
>
>  from .i18n import _
> @@ -144,9 +143,7 @@ def _posixworker(ui, func, staticargs, a
>      os.close(wfd)
>      fp = os.fdopen(rfd, 'rb', 0)
> -    t = threading.Thread(target=waitforworkers)
> -    t.start()
>      def cleanup():
>          signal.signal(signal.SIGINT, oldhandler)
> -        t.join()
> +        waitforworkers()
>          signal.signal(signal.SIGCHLD, oldchldhandler)
>          status = problem[0]
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