[Boost-bugs] [Boost C++ Libraries] #4162: io_service can't be used correctly after fork().

Subject: [Boost-bugs] [Boost C++ Libraries] #4162: io_service can't be used correctly after fork().
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-04-28 20:44:39

#4162: io_service can't be used correctly after fork().
----------------------------------+-----------------------------------------
 Reporter:  artyomtnk@…           |       Owner:  chris_kohlhoff
     Type:  Bugs                  |      Status:  new           
Milestone:  Boost 1.43.0          |   Component:  asio          
  Version:  Boost 1.42.0          |    Severity:  Problem       
 Keywords:  asio posix fork unix  |  
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 Hello,

 I'm trying to run standard "prefork" unix configuration with
 boost-asio.

 I have following setup:

 1. I bind to some port.

 2. I prefork several processes.

 3. As new connection is avalible one of processes accept it
 and run the main loop.


 ---------------------
 Issue:

 The io_service is created at the begging and creates
 eventfd (or pipe), and unlike devpoll, kqueue or epoll it is
 shared between forked processes.


 ---------------------
 There is the problem:

 When one thread in process try to "post" something to event
 loop it interrupts the select with evenfd... And accidentially
 other process may actually receive this notification and wake up
 when the main process that should receive notification does not.

 ---------------------
 In short

 If io_service was created before fork(), post() member function
 would not work correctly.

 ---------------------
 Solutions:

 1) Postpone creation of pipe/eventfd to the stage when run()
 is called instead of construction of io_service.
 2) Reopen interrupter if fork() was called.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4162>
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