[PATCH 7 of 8 V4] worker: add a SIGCHLD handler to collect worker immediately

[Yuya Nishihara]

On Sat, 12 Nov 2016 03:11:38 +0000, Jun Wu wrote:
> # HG changeset patch
> # User Jun Wu <quark at fb.com>
> # Date 1478920042 0
> #      Sat Nov 12 03:07:22 2016 +0000
> # Node ID 7492186538a69cdfad28cb93093d7f7077942ca3
> # Parent  596cee9d5c12dcfa2d272b5441d5060a26a6440c
> # Available At https://bitbucket.org/quark-zju/hg-draft
> #              hg pull https://bitbucket.org/quark-zju/hg-draft -r 7492186538a6
> worker: add a SIGCHLD handler to collect worker immediately
> 
> As planned by previous patches, add a SIGCHLD handler to get notifications
> about worker exits, and deals with worker failure immediately.
> 
> diff --git a/mercurial/worker.py b/mercurial/worker.py
> --- a/mercurial/worker.py
> +++ b/mercurial/worker.py
> @@ -126,8 +126,12 @@ def _posixworker(ui, func, staticargs, a
>                  problem[0] = st
>                  killworkers()
> +    def sigchldhandler(signum, frame):
> +        waitforworkers(blocking=False)
> +    oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler)
>      for pargs in partition(args, workers):
>          pid = os.fork()
>          if pid == 0:
>              signal.signal(signal.SIGINT, oldhandler)
> +            signal.signal(signal.SIGCHLD, oldchldhandler)
>              try:
>                  os.close(rfd)
> @@ -147,4 +151,5 @@ def _posixworker(ui, func, staticargs, a
>          signal.signal(signal.SIGINT, oldhandler)
>          t.join()
> +        signal.signal(signal.SIGCHLD, oldchldhandler)

I got strange error:

% hg up --trace
Traceback (most recent call last):
  ...
  File "mercurial/merge.py", line 1187, in applyupdates
    for i, item in prog:
  File "mercurial/worker.py", line 159, in _posixworker
    for line in fp:
IOError: [Errno 0] Error
abort: Error

Maybe something goes wrong in the buffered iterator?
iter(fp.readline, '') worked fine.