[PATCH 6 of 7 V3] worker: test and set problem[0] atomically

Jun Wu quark at fb.com
Sat Aug 6 07:09:07 EDT 2016


Excerpts from Augie Fackler's message of 2016-08-05 14:22:09 -0400:
> On Thu, Aug 04, 2016 at 07:29:07PM +0100, Jun Wu wrote:
> > # HG changeset patch
> > # User Jun Wu <quark at fb.com>
> > # Date 1470334096 -3600
> > #      Thu Aug 04 19:08:16 2016 +0100
> > # Node ID d08d72f5d8bf302dd1231be410d0b23dc082eb66
> > # Parent  d179a66b0b15988687ba9d69c5b76e4464a457eb
> > # Available At https://bitbucket.org/quark-zju/hg-draft 
> > #              hg pull https://bitbucket.org/quark-zju/hg-draft  -r d08d72f5d8bf
> > worker: test and set problem[0] atomically
> >
> > Previously problem[0] is not tested and set atomically:
> >
> >     if st and not problem[0]:
> >         # at this time, another SIGCHILD happens, killworkers may run twice
> >         problem[0] = st
> >         killworkers()
> >
> > This patch addresses the issue by using itertools.count(). Its CPython
> > implementation will make it "atomic" at the Python code level, which is
> > enough for our use-case (signal handler).
> 
> This is very clever, but:
> 
> 1) pypy is already a thing

I just got confirmation by arigato on #pypy that this also works in Pypy.
Same to "set.pop()". I will use the later so address the "send SIGTERM
to waited processes" issue and mention Pypy in commit message.

Cheers!


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