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* [Bug libstdc++/54562] New: mutex and condition variable timers
@ 2012-09-13  2:19 zoltan at epochcapital dot com.au
  2012-09-13  2:24 ` [Bug libstdc++/54562] " zoltan at epochcapital dot com.au
                   ` (4 more replies)
  0 siblings, 5 replies; 6+ messages in thread
From: zoltan at epochcapital dot com.au @ 2012-09-13  2:19 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

             Bug #: 54562
           Summary: mutex and condition variable timers
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zoltan@epochcapital.com.au


Created attachment 28182
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28182
std::timed_mutex::try_lock_for test

Hello,

1., When using std::timed_mutex::try_lock_for() with high precision timers
enabled on Linux the method will return immediately, rather than after the
given time duration has elapsed. This is because it uses the CLOCK_MONOTONIC
clock (if available on the platform) to calculate the absolute time when it
needs to return, which is incorrect as the POSIX pthread_mutex_timedlock() call
uses the CLOCK_REALTIME clock, and on my platform the monotonic clock is way
behind the real time clock. 

Please see the attached cpptest.cpp file to reproduce the problem:
$ g++-4.7.1 -std=gnu++11 cpptest.cpp -o cpptest
$ ./cpptest 
mutex locked
delay: 0

It should have displayed "delay: 3" instead.

2., std::condition_variable uses the std::chrono::system_clock for timed waits,
I suggest changing that to std::chrono::high_resolution_clock which has the
same precision as the POSIX pthread_cond_timedwait() function.

My platform:
# uname -a
Linux epcau-srv-dev 2.6.33.7-rt29-0.5-rt #1 SMP PREEMPT RT 2010-08-25 19:40:23
+0200 x86_64 x86_64 x86_64 GNU/Linux
# g++-4.7.1 -v
Reading specs from /opt/epoch/lib64/gcc/x86_64-suse-linux/4.7.1/specs
COLLECT_GCC=g++-4.7.1
COLLECT_LTO_WRAPPER=/opt/epoch/lib64/gcc/x86_64-suse-linux/4.7.1/lto-wrapper
Target: x86_64-suse-linux
Configured with: ../gcc-4.7.1-mutex/configure --build=x86_64-suse-linux
--prefix=/opt/epoch --libdir=/opt/epoch/lib64 --libexecdir=/opt/epoch/lib64
--with-slibdir=/opt/epoch/lib64/gcc/x86_64-suse-linux/4.7.1/libgcc/lib64
--with-gxx-include-dir=/opt/epoch/include/c++/4.7.1 --program-suffix=-4.7.1
--enable-version-specific-runtime-libs --enable-languages=c++ --disable-nls
--disable-libssp --enable-__cxa_atexit --with-system-zlib --enable-gold
--with-plugin-ld=/usr/bin/gold --enable-lto --enable-libstdcxx-time=rt
--enable-linux-futex --enable-libstdcxx-threads --enable-libstdcxx-debug
--enable-libstdcxx-allocator=new
Thread model: posix
gcc version 4.7.1 (GCC)


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [Bug libstdc++/54562] mutex and condition variable timers
  2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
@ 2012-09-13  2:24 ` zoltan at epochcapital dot com.au
  2012-10-08 19:55 ` redi at gcc dot gnu.org
                   ` (3 subsequent siblings)
  4 siblings, 0 replies; 6+ messages in thread
From: zoltan at epochcapital dot com.au @ 2012-09-13  2:24 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

--- Comment #1 from Zoltan Glozik <zoltan at epochcapital dot com.au> 2012-09-13 02:24:24 UTC ---
Created attachment 28183
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28183
suggested patch


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [Bug libstdc++/54562] mutex and condition variable timers
  2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
  2012-09-13  2:24 ` [Bug libstdc++/54562] " zoltan at epochcapital dot com.au
@ 2012-10-08 19:55 ` redi at gcc dot gnu.org
  2012-10-08 22:11 ` zoltan at epochcapital dot com.au
                   ` (2 subsequent siblings)
  4 siblings, 0 replies; 6+ messages in thread
From: redi at gcc dot gnu.org @ 2012-10-08 19:55 UTC (permalink / raw)
  To: gcc-bugs


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-10-08
     Ever Confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-08 19:55:28 UTC ---
Thanks for the report, Zoltan, it's on my list to look at asap.


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [Bug libstdc++/54562] mutex and condition variable timers
  2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
  2012-09-13  2:24 ` [Bug libstdc++/54562] " zoltan at epochcapital dot com.au
  2012-10-08 19:55 ` redi at gcc dot gnu.org
@ 2012-10-08 22:11 ` zoltan at epochcapital dot com.au
  2013-11-11 13:33 ` redi at gcc dot gnu.org
  2013-11-11 13:35 ` redi at gcc dot gnu.org
  4 siblings, 0 replies; 6+ messages in thread
From: zoltan at epochcapital dot com.au @ 2012-10-08 22:11 UTC (permalink / raw)
  To: gcc-bugs


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

--- Comment #3 from Zoltan Glozik <zoltan at epochcapital dot com.au> 2012-10-08 22:11:26 UTC ---
Thanks Jon, how weird to communicate with you on the gcc mailing lists...

I hope you are doing well.

Cheers,
Zoltan

> -----Original Message-----
> From: redi at gcc dot gnu.org [mailto:gcc-bugzilla@gcc.gnu.org]
> Sent: Tuesday, 9 October 2012 6:55 AM
> To: zoltan@epochcapital.com.au
> Subject: [Bug libstdc++/54562] mutex and condition variable timers
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562
>
> Jonathan Wakely <redi at gcc dot gnu.org> changed:
>
>            What    |Removed                     |Added
> --------------------------------------------------------------------------
> --
>              Status|UNCONFIRMED                 |NEW
>    Last reconfirmed|                            |2012-10-08
>      Ever Confirmed|0                           |1
>
> --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-08
> 19:55:28 UTC ---
> Thanks for the report, Zoltan, it's on my list to look at asap.
>
> --
> Configure bugmail: http://gcc.gnu.org/bugzilla/userprefs.cgi?tab=email
> ------- You are receiving this mail because: -------
> You reported the bug.


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [Bug libstdc++/54562] mutex and condition variable timers
  2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
                   ` (2 preceding siblings ...)
  2012-10-08 22:11 ` zoltan at epochcapital dot com.au
@ 2013-11-11 13:33 ` redi at gcc dot gnu.org
  2013-11-11 13:35 ` redi at gcc dot gnu.org
  4 siblings, 0 replies; 6+ messages in thread
From: redi at gcc dot gnu.org @ 2013-11-11 13:33 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Mon Nov 11 13:33:48 2013
New Revision: 204672

URL: http://gcc.gnu.org/viewcvs?rev=204672&root=gcc&view=rev
Log:
    PR libstdc++/54562
    * include/std/mutex (__timed_mutex_impl::__clock_t): Use
    high_resolution_clock for absolute timeouts, because
    pthread_mutex_timedlock uses CLOCK_REALTIME not CLOCK_MONOTONIC.
    (__timed_mutex_impl::_M_try_lock_for): Use steady_clock for relative
    timeouts as per [thread.req.timing].
    (__timed_mutex_impl::_M_try_lock_until<Clock,Duration>): Convert to
    __clock_t time point instead of using _M_try_lock_for.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/mutex


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [Bug libstdc++/54562] mutex and condition variable timers
  2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
                   ` (3 preceding siblings ...)
  2013-11-11 13:33 ` redi at gcc dot gnu.org
@ 2013-11-11 13:35 ` redi at gcc dot gnu.org
  4 siblings, 0 replies; 6+ messages in thread
From: redi at gcc dot gnu.org @ 2013-11-11 13:35 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54562

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.9.0

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 4.9.0.

We still don't handle clock adjustments, doing so requires looping which adds
overhead that might not be desirable. I'll revisit that topic another time.


^ permalink raw reply	[flat|nested] 6+ messages in thread
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2012-09-13  2:19 [Bug libstdc++/54562] New: mutex and condition variable timers zoltan at epochcapital dot com.au
2012-09-13  2:24 ` [Bug libstdc++/54562] " zoltan at epochcapital dot com.au
2012-10-08 19:55 ` redi at gcc dot gnu.org
2012-10-08 22:11 ` zoltan at epochcapital dot com.au
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