ad4d1d21ad
The pthread_cond_clockwait 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++/41861 by supporting std::chrono::steady_clock properly with std::condition_variable. This means that code using std::condition_variable::wait_for or std::condition_variable::wait_until with std::chrono::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_cond_clockwait is available then std::chrono::steady_clock is deemed to be the "best" clock available which means that it is used for the relative wait_for calls and absolute wait_until calls using user-defined clocks. Calls explicitly using std::chrono::system_clock continue to use CLOCK_REALTIME via __gthread_cond_timedwait. If pthread_cond_clockwait is not available then std::chrono::system_clock is deemed to be the "best" clock available which means that the previous suboptimal behaviour remains. 2019-09-04 Mike Crowe <mac@mcrowe.com> PR libstdc++/41861 * acinclude.m4 (GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT): Check for new pthread_cond_clockwait function. * configure.ac: Use GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT. * configure: Regenerate. * config.h.in: Regenerate. * include/std/condition_variable: (condition_variable): Rename __steady_clock_t typedef and add system_clock. Change __clock_t to be a typedef for the preferred clock to convert arbitrary other clocks to. [_GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT] (wait_until): Add a steady_clock overload. (wait_until): Change __clock_t overload to use system_clock. [_GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT] (__wait_until_impl): Add steady_clock overload that calls pthread_cond_clockwait. (__wait_until_impl): Change __clock_t overload to use system_clock. (condition_variable_any) [_GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT]: Use steady_clock for __clock_t if pthread_cond_clockwait is available. From-SVN: r275390 |
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