Re: [Boost-bugs] [Boost C++ Libraries] #11377: Boost condition variable always waits for system clock deadline

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11377: Boost condition variable always waits for system clock deadline
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-09-08 23:06:18

#11377: Boost condition variable always waits for system clock deadline
-------------------------------------+-------------------------------------
  Reporter:  Dave Bacher             |      Owner:  viboes
  <dbacher@…>                        |     Status:  assigned
      Type:  Bugs                    |  Component:  thread
 Milestone:  To Be Determined        |   Severity:  Problem
   Version:  Boost 1.56.0            |   Keywords:  condition variable,
Resolution:                          |  clock
-------------------------------------+-------------------------------------

Comment (by Dave Bacher <dbacher@…>):

 The patch is working properly for me.

 With #define BOOST_THREAD_HAS_CONDATTR_SET_CLOCK_MONOTONIC, the test code
 waits for the specified duration even with the adjustment of the system
 clock. In the output below, the test completes after 5 seconds even though
 the system clock was adjusted backwards. Previously, the test would hang
 until the system clock reached the time the test was started plus 5
 seconds.

 {{{
 $ sh clock_changes_test.sh
 [sudo] password:
 Setup sudo authentication
 Starting test to wait for 5 seconds
 Adjusting time to 01:00:00
 Waiting for 5 sec
 WAIT_UNTIL
 Tue Sep  8 01:00:00 PDT 2015
 Waiting...
 Steady duration/start/stop: 5
    3104032404935 nanoseconds since boot / 3109032558479 nanoseconds since
 boot
 System duration/start/stop: -52747 seconds
    1441751952904865440 nanoseconds since Jan 1, 1970 / 1441699204998073008
 nanoseconds since Jan 1, 1970
 Test complete, please check your system clock
 Tue Sep  8 01:00:05 PDT 2015
 }}}

 Regarding when to use the monotonic clock, I think there are separate two
 issues:
 1. Policy -- when should the monotonic clock be used? I would prefer that
 using the monotonic clock is the default. But perhaps other applications
 have other expectations.

 2. Availability -- how to determine if the monotonic clock is available?
 On my Linux system, linux/time.h #defines CLOCK_MONOTONIC. At runtime,
 [http://linux.die.net/man/3/clock_gettime clock_gettime] returns an error
 if the specified clock id is not available.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11377#comment:11>
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