[Boost-bugs] [Boost C++ Libraries] #6377: Condition variable blocks when changing time

Subject: [Boost-bugs] [Boost C++ Libraries] #6377: Condition variable blocks when changing time
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-01-11 09:55:33

#6377: Condition variable blocks when changing time
-------------------------------------------------+--------------------------
 Reporter:  Johan Borkhuis <johan@…>             |       Owner:  igaztanaga  
     Type:  Bugs                                 |      Status:  new         
Milestone:  To Be Determined                     |   Component:  interprocess
  Version:  Boost 1.47.0                         |    Severity:  Problem     
 Keywords:  condition variable                   |  
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 I am using Linux on an ARM system, running Boost 1.47. My application
 needs accurate timing, and for this I use a POSIX timer using SIGRTMIN.
 This part is not something that I can control, it is an external library
 that implements this. I use condition variables as a timing mechanism
 within my software.

 When I use condition variables without the POSIX timer there is no
 problem. The timing continues correctly, even if I change the time forward
 or backward.

 When I start the POSIX timer the condition variable does not time-out when
 I change the time backward. It only times out when the original time (plus
 timeout) is reached.

 When I changed the clock of the pthread condition variable to monotonic
 (call to pthread_condattr_setclock(&condattr, CLOCK_MONOTONIC)) the result
 was OK
 again.

 Attached is a test application that shows the problem and implements a
 solution. This solution is not within the Boost library but directly as a
 POSIX condition variable.
 Options to the test application:
 {{{
 -b: use boost condition variable
 -s: generate POSIX signals
 }}}

 When running the testapplication with -bs the application will stop
 reporting when the time is changed backwards. When the time is set back to
 a time after the time the time was changed the application will continue.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6377>
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