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| author | Mike Crowe <mac@mcrowe.com> | 2019-12-02 16:23:01 +0000 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-12-02 16:23:01 +0000 |
| commit | 3b2fb54353d29ae7c6067ebc78549d1296b1340d (patch) | |
| tree | 3557a7cadb98bc8fb7c149ffce9100ffac6dc627 /libstdc++-v3/config.h.in | |
| parent | 49638674a46e58ff8bfb41c5346386dca9569375 (diff) | |
| download | gcc-3b2fb54353d29ae7c6067ebc78549d1296b1340d.zip gcc-3b2fb54353d29ae7c6067ebc78549d1296b1340d.tar.gz gcc-3b2fb54353d29ae7c6067ebc78549d1296b1340d.tar.bz2 | |
libstdc++: PR 78237 Add full steady_clock support to timed_mutex
The pthread_mutex_clocklock function is available in glibc since the
2.30 release. If this function is available in the C library it can be
used to fix PR libstdc++/78237 by supporting steady_clock properly with
timed_mutex.
This means that code using timed_mutex::try_lock_for or
timed_mutex::wait_until with steady_clock is no longer subject to timing
out early or potentially waiting for much longer if the system clock is
warped at an inopportune moment.
If pthread_mutex_clocklock is available then steady_clock is deemed to
be the "best" clock available which means that it is used for the
relative try_lock_for calls and absolute try_lock_until calls using
steady_clock and user-defined clocks. Calls explicitly using
system_clock (aka high_resolution_clock) continue to use CLOCK_REALTIME
via __gthread_cond_timedwait.
If pthread_mutex_clocklock is not available then system_clock is deemed
to be the "best" clock available which means that the previous
suboptimal behaviour remains.
2019-12-02 Mike Crowe <mac@mcrowe.com>
PR libstdc++/78237 Add full steady_clock support to timed_mutex
* acinclude.m4 (GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK): Define to
detect presence of pthread_mutex_clocklock function.
* config.h.in: Regenerate.
* configure: Regenerate.
* configure.ac: Call GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK.
* include/std/mutex (__timed_mutex_impl): Remove unnecessary __clock_t.
(__timed_mutex_impl::_M_try_lock_for): Use best clock to turn relative
timeout into absolute timeout.
(__timed_mutex_impl::_M_try_lock_until): Keep existing implementation
for system_clock. Add new implementation for steady_clock that calls
_M_clocklock. Modify overload for user-defined clock to use a relative
wait so that it automatically uses the best clock.
[_GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK] (timed_mutex::_M_clocklock):
New member function.
(recursive_timed_mutex::_M_clocklock): Likewise.
From-SVN: r278901
Diffstat (limited to 'libstdc++-v3/config.h.in')
| -rw-r--r-- | libstdc++-v3/config.h.in | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in index 32f7863..3d51534 100644 --- a/libstdc++-v3/config.h.in +++ b/libstdc++-v3/config.h.in @@ -1002,6 +1002,9 @@ /* Define if pthread_cond_clockwait is available in <pthread.h>. */ #undef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT +/* Define if pthread_mutex_clocklock is available in <pthread.h>. */ +#undef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK + /* Define if POSIX read/write locks are available in <gthr.h>. */ #undef _GLIBCXX_USE_PTHREAD_RWLOCK_T |