Re: [Boost-bugs] [Boost C++ Libraries] #7611: segfault in epoll_reactor.ipp

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #7611: segfault in epoll_reactor.ipp
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-01-30 16:45:32

#7611: segfault in epoll_reactor.ipp
-------------------------------------------------+-------------------------
  Reporter:  Fredrik Jansson                     |      Owner:
  <fredrik.jansson.se@…>                         |  chris_kohlhoff
      Type:  Bugs                                |     Status:  closed
 Milestone:  To Be Determined                    |  Component:  asio
   Version:  Boost 1.52.0                        |   Severity:  Problem
Resolution:  invalid                             |   Keywords:
-------------------------------------------------+-------------------------

Comment (by anonymous):

 Replying to [comment:5 anonymous]:
 > Replying to [comment:4 jyu@…]:
 > > In my case, the crash is due to two threads simultaneously closing the
 socket. can you make the socket close or shutdown function thread-safe,
 just as Fredrik Jansson suggested?
 >
 > You have a threading issue that's even worse than that of the original
 poster. And it's your all your own fault.
 >
 > Here's how you can solve it: Use a mutex, such that you do NOT have 2
 threads messing with the socket at the same time. (Within the protected
 region, you could find out if the socket-descriptor is already closed, by
 using something like descriptor.is_open() , see
 http://www.boost.org/doc/libs/1_63_0/doc/html/boost_asio/reference.html#boost_asio.reference.posix__basic_descriptor.is_open

 )


 I ended up doing compare-and-swap on a flag to make sure the close-socket
 is called only once.

 Just wondering that the asio close-socket function may be thread-safe by
 using the compare-and-swap on that crashing pointer.

 In my app, only those thread-safe asio socket functions have been used
 concurrently. I did not realized that the asio close-socket function is an
 exception. My bad, I did not read the doc carefully.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7611#comment:6>
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