libstdc++: Add full steady_clock support to shared_timed_mutex
The pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock functions were added to glibc in v2.30. They have also been added to Android Bionic. If these functions are available in the C library then they can be used to implement shared_timed_mutex::try_lock_until, shared_timed_mutex::try_lock_for, shared_timed_mutex::try_lock_shared_until and shared_timed_mutex::try_lock_shared_for so that they are no longer unaffected by the system clock being warped. (This is the shared_mutex equivalent of PR libstdc++/78237 for mutex.) If the new functions are 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. It's not possible to have _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK defined without _GLIBCXX_USE_PTHREAD_RWLOCK_T, so the requirement that the clock be the same as condition_variable is maintained. Calls explicitly using system_clock (aka high_resolution_clock) continue to use CLOCK_REALTIME via the old pthread_rwlock_timedrdlock and pthread_rwlock_timedwrlock functions. If the new functions are not available then system_clock is deemed to be the "best" clock available which means that the previous suboptimal behaviour remains. Additionally, the user-defined clock used with shared_timed_mutex::try_lock_for and shared_mutex::try_lock_shared_for may have higher precision than __clock_t. We may need to round the duration up to ensure that the timeout is long enough. (See __timed_mutex_impl::_M_try_lock_for) 2019-12-02 Mike Crowe <mac@mcrowe.com> Add full steady_clock support to shared_timed_mutex * acinclude.m4 (GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK): Define to check for the presence of both pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock. * config.h.in: Regenerate. * configure.ac: Call GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK. * configure: Regenerate. * include/std/shared_mutex (shared_timed_mutex): Define __clock_t as the best clock to use for relative waits. (shared_timed_mutex::try_lock_for) Round up wait duration if necessary. (shared_timed_mutex::try_lock_shared_for): Likewise. (shared_timed_mutex::try_lock_until): Use existing try_lock_until implementation for system_clock (which matches __clock_t when _GLIBCCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK is not defined). Add new overload for steady_clock that uses pthread_rwlock_clockwrlock if it is available. Simplify overload for non-standard clock to just call try_lock_for with a relative timeout. (shared_timed_mutex::try_lock_shared_until): Likewise. From-SVN: r278903
This commit is contained in:
Mike Crowe
Jonathan Wakely
parent
a7334019b1
commit
ab40695a46
6 changed files with 226 additions and 21 deletions
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@ -1,5 +1,24 @@
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2019-12-02 Mike Crowe <mac@mcrowe.com>
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Add full steady_clock support to shared_timed_mutex
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* acinclude.m4 (GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK): Define
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to check for the presence of both pthread_rwlock_clockrdlock and
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pthread_rwlock_clockwrlock.
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* config.h.in: Regenerate.
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* configure.ac: Call GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK.
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* configure: Regenerate.
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* include/std/shared_mutex (shared_timed_mutex): Define __clock_t as
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the best clock to use for relative waits.
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(shared_timed_mutex::try_lock_for) Round up wait duration if necessary.
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(shared_timed_mutex::try_lock_shared_for): Likewise.
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(shared_timed_mutex::try_lock_until): Use existing try_lock_until
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implementation for system_clock (which matches __clock_t when
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_GLIBCCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK is not defined). Add new
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overload for steady_clock that uses pthread_rwlock_clockwrlock if it
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is available. Simplify overload for non-standard clock to just call
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try_lock_for with a relative timeout.
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(shared_timed_mutex::try_lock_shared_until): Likewise.
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PR libstdc++/91906 Fix timed_mutex::try_lock_until on arbitrary clock
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* include/std/mutex (__timed_mutex_impl::_M_try_lock_until): Loop
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until the absolute timeout time is reached as measured against the
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@ -4258,6 +4258,39 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK], [
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AC_LANG_RESTORE
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])
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dnl
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dnl Check whether pthread_mutex_clocklock is available in <pthread.h> for std::timed_mutex to use,
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dnl and define _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK.
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dnl
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AC_DEFUN([GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK], [
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AC_LANG_SAVE
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AC_LANG_CPLUSPLUS
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ac_save_CXXFLAGS="$CXXFLAGS"
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CXXFLAGS="$CXXFLAGS -fno-exceptions"
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ac_save_LIBS="$LIBS"
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LIBS="$LIBS -lpthread"
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AC_MSG_CHECKING([for pthread_rwlock_clockrdlock, pthread_wlock_clockwrlock])
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AC_CACHE_VAL(glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK, [
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GCC_TRY_COMPILE_OR_LINK(
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[#include <pthread.h>],
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[pthread_rwlock_t rwl; struct timespec ts;]
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[int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);]
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[int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);],
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[glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes],
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[glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=no])
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])
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if test $glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK = yes; then
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AC_DEFINE(_GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK, 1, [Define if pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock are available in <pthread.h>.])
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fi
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AC_MSG_RESULT($glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK)
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CXXFLAGS="$ac_save_CXXFLAGS"
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LIBS="$ac_save_LIBS"
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AC_LANG_RESTORE
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])
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dnl
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dnl Check whether sysctl is available in <pthread.h>, and define _GLIBCXX_USE_SYSCTL_HW_NCPU.
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dnl
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@ -1005,6 +1005,10 @@
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/* Define if pthread_mutex_clocklock is available in <pthread.h>. */
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#undef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
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/* Define if pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock are
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available in <pthread.h>. */
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#undef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
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/* Define if POSIX read/write locks are available in <gthr.h>. */
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#undef _GLIBCXX_USE_PTHREAD_RWLOCK_T
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87
libstdc++-v3/configure
vendored
87
libstdc++-v3/configure
vendored
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@ -21963,6 +21963,93 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
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# For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
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ac_ext=cpp
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ac_cpp='$CXXCPP $CPPFLAGS'
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ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
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ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
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ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
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ac_save_CXXFLAGS="$CXXFLAGS"
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CXXFLAGS="$CXXFLAGS -fno-exceptions"
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ac_save_LIBS="$LIBS"
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LIBS="$LIBS -lpthread"
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_rwlock_clockrdlock, pthread_wlock_clockwrlock" >&5
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$as_echo_n "checking for pthread_rwlock_clockrdlock, pthread_wlock_clockwrlock... " >&6; }
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if ${glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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if test x$gcc_no_link = xyes; then
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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#include <pthread.h>
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int
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main ()
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{
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pthread_rwlock_t rwl; struct timespec ts;
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int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);
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int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);
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;
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return 0;
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}
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_ACEOF
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if ac_fn_cxx_try_compile "$LINENO"; then :
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glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes
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else
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glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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else
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if test x$gcc_no_link = xyes; then
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as_fn_error $? "Link tests are not allowed after GCC_NO_EXECUTABLES." "$LINENO" 5
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fi
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cat confdefs.h - <<_ACEOF >conftest.$ac_ext
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/* end confdefs.h. */
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#include <pthread.h>
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int
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main ()
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{
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pthread_rwlock_t rwl; struct timespec ts;
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int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);
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int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);
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;
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return 0;
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}
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_ACEOF
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if ac_fn_cxx_try_link "$LINENO"; then :
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glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes
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else
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glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=no
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fi
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rm -f core conftest.err conftest.$ac_objext \
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conftest$ac_exeext conftest.$ac_ext
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fi
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fi
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if test $glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK = yes; then
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$as_echo "#define _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK 1" >>confdefs.h
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK" >&5
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$as_echo "$glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK" >&6; }
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CXXFLAGS="$ac_save_CXXFLAGS"
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LIBS="$ac_save_LIBS"
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ac_ext=c
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ac_cpp='$CPP $CPPFLAGS'
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ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
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ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
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ac_compiler_gnu=$ac_cv_c_compiler_gnu
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ac_fn_c_check_header_mongrel "$LINENO" "locale.h" "ac_cv_header_locale_h" "$ac_includes_default"
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if test "x$ac_cv_header_locale_h" = xyes; then :
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@ -228,6 +228,9 @@ GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT
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# For pthread_mutex_clocklock
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GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK
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# For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
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GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK
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AC_LC_MESSAGES
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# For hardware_concurrency
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@ -450,7 +450,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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using _Base = __shared_timed_mutex_base;
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// Must use the same clock as condition_variable for __shared_mutex_cv.
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typedef chrono::system_clock __clock_t;
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#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
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using __clock_t = chrono::steady_clock;
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#else
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using __clock_t = chrono::system_clock;
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#endif
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public:
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shared_timed_mutex() = default;
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@ -467,9 +471,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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template<typename _Rep, typename _Period>
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bool
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try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
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try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
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{
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return try_lock_until(__clock_t::now() + __rel_time);
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auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
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if (ratio_greater<__clock_t::period, _Period>())
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++__rt;
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return try_lock_until(__clock_t::now() + __rt);
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}
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// Shared ownership
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@ -480,9 +487,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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template<typename _Rep, typename _Period>
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bool
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try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
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try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rtime)
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{
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return try_lock_shared_until(__clock_t::now() + __rel_time);
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auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
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if (ratio_greater<__clock_t::period, _Period>())
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++__rt;
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return try_lock_shared_until(__clock_t::now() + __rt);
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}
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#if _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
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@ -491,7 +501,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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template<typename _Duration>
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bool
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try_lock_until(const chrono::time_point<__clock_t, _Duration>& __atime)
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try_lock_until(const chrono::time_point<chrono::system_clock,
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_Duration>& __atime)
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{
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
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auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
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@ -512,23 +523,47 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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return true;
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}
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#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
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template<typename _Duration>
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bool
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try_lock_until(const chrono::time_point<chrono::steady_clock,
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_Duration>& __atime)
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{
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
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auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
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__gthread_time_t __ts =
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{
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static_cast<std::time_t>(__s.time_since_epoch().count()),
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static_cast<long>(__ns.count())
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};
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int __ret = pthread_rwlock_clockwrlock(&_M_rwlock, CLOCK_MONOTONIC,
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&__ts);
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// On self-deadlock, we just fail to acquire the lock. Technically,
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// the program violated the precondition.
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if (__ret == ETIMEDOUT || __ret == EDEADLK)
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return false;
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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return true;
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}
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#endif
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template<typename _Clock, typename _Duration>
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bool
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try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
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try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
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{
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// DR 887 - Sync unknown clock to known clock.
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const typename _Clock::time_point __c_entry = _Clock::now();
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const __clock_t::time_point __s_entry = __clock_t::now();
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const auto __delta = __abs_time - __c_entry;
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const auto __s_atime = __s_entry + __delta;
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return try_lock_until(__s_atime);
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typename _Clock::time_point __now = _Clock::now();
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auto __rtime = __atime - __now;
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return try_lock_for(__rtime);
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}
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// Shared ownership
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template<typename _Duration>
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bool
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try_lock_shared_until(const chrono::time_point<__clock_t,
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try_lock_shared_until(const chrono::time_point<chrono::system_clock,
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_Duration>& __atime)
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{
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
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@ -564,17 +599,41 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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return true;
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}
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#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
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template<typename _Duration>
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bool
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try_lock_shared_until(const chrono::time_point<chrono::steady_clock,
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_Duration>& __atime)
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{
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
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auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
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__gthread_time_t __ts =
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{
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static_cast<std::time_t>(__s.time_since_epoch().count()),
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static_cast<long>(__ns.count())
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};
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int __ret = pthread_rwlock_clockrdlock(&_M_rwlock, CLOCK_MONOTONIC,
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&__ts);
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// On self-deadlock, we just fail to acquire the lock. Technically,
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// the program violated the precondition.
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if (__ret == ETIMEDOUT || __ret == EDEADLK)
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return false;
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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return true;
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}
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#endif
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template<typename _Clock, typename _Duration>
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bool
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try_lock_shared_until(const chrono::time_point<_Clock,
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_Duration>& __abs_time)
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_Duration>& __atime)
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{
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// DR 887 - Sync unknown clock to known clock.
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const typename _Clock::time_point __c_entry = _Clock::now();
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const __clock_t::time_point __s_entry = __clock_t::now();
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const auto __delta = __abs_time - __c_entry;
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const auto __s_atime = __s_entry + __delta;
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return try_lock_shared_until(__s_atime);
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typename _Clock::time_point __now = _Clock::now();
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auto __rtime = __atime - __now;
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return try_lock_shared_for(__rtime);
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}
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#else // ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
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