[PATCH 05/11] PR libstdc++/78237 Add full steady_clock support to timed_mutex
Mike Crowe
mac@mcrowe.com
Sat Sep 28 08:45:00 GMT 2019
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.
* acinclude.m4: Define GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK to
detect presence of pthread_mutex_clocklock function.
* config.h.in: Add _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK define.
* configure.ac: Call GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK.
* configure: Add generated part to detect pthread_mutex_clocklock
function.
* include/std/mutex (__timed_mutex_impl): Remove unnecessary
__clock_t. (_M_try_lock_for) Use best clock to
turn relative timeout into absolute timeout. (_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.
* include/std/mutex (timed_mutex): If pthread_mutex_clocklock is
available, add _M_clocklock method that calls it.
* include/std/mutex (recursive_timed_mutex): Likewise.
---
libstdc++-v3/acinclude.m4 | 31 +++++++++++++-
libstdc++-v3/config.h.in | 3 +-
libstdc++-v3/configure | 82 +++++++++++++++++++++++++++++++++++-
libstdc++-v3/configure.ac | 3 +-
libstdc++-v3/include/std/mutex | 49 +++++++++++++++++----
5 files changed, 160 insertions(+), 8 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index ad2cb01..9ecfa96 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4228,6 +4228,37 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT], [
])
dnl
+dnl Check whether pthread_mutex_clocklock is available in <pthread.h> for std::timed_mutex to use,
+dnl and define _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK.
+dnl
+AC_DEFUN([GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK], [
+
+ AC_LANG_SAVE
+ AC_LANG_CPLUSPLUS
+ ac_save_CXXFLAGS="$CXXFLAGS"
+ CXXFLAGS="$CXXFLAGS -fno-exceptions"
+ ac_save_LIBS="$LIBS"
+ LIBS="$LIBS -lpthread"
+
+ AC_MSG_CHECKING([for pthread_mutex_clocklock])
+ AC_CACHE_VAL(glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK, [
+ GCC_TRY_COMPILE_OR_LINK(
+ [#include <pthread.h>],
+ [pthread_mutex_t mutex; struct timespec ts; int n = pthread_mutex_clocklock(&mutex, CLOCK_REALTIME, &ts);],
+ [glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=yes],
+ [glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=no])
+ ])
+ if test $glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK = yes; then
+ AC_DEFINE(_GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK, 1, [Define if pthread_mutex_clocklock is available in <pthread.h>.])
+ fi
+ AC_MSG_RESULT($glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK)
+
+ CXXFLAGS="$ac_save_CXXFLAGS"
+ LIBS="$ac_save_LIBS"
+ AC_LANG_RESTORE
+])
+
+dnl
dnl Check whether sysctl is available in <pthread.h>, and define _GLIBCXX_USE_SYSCTL_HW_NCPU.
dnl
AC_DEFUN([GLIBCXX_CHECK_SYSCTL_HW_NCPU], [
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index 3d13402..9670176 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -994,6 +994,9 @@
/* 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
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index e646c41..41df34c 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -21677,6 +21677,88 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
+# For pthread_mutex_clocklock
+
+
+
+ ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+ ac_save_CXXFLAGS="$CXXFLAGS"
+ CXXFLAGS="$CXXFLAGS -fno-exceptions"
+ ac_save_LIBS="$LIBS"
+ LIBS="$LIBS -lpthread"
+
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_mutex_clocklock" >&5
+$as_echo_n "checking for pthread_mutex_clocklock... " >&6; }
+ if ${glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+
+ if test x$gcc_no_link = xyes; then
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <pthread.h>
+int
+main ()
+{
+pthread_mutex_t mutex; struct timespec ts; int n = pthread_mutex_clocklock(&mutex, CLOCK_REALTIME, &ts);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=yes
+else
+ glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+ if test x$gcc_no_link = xyes; then
+ as_fn_error $? "Link tests are not allowed after GCC_NO_EXECUTABLES." "$LINENO" 5
+fi
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <pthread.h>
+int
+main ()
+{
+pthread_mutex_t mutex; struct timespec ts; int n = pthread_mutex_clocklock(&mutex, CLOCK_REALTIME, &ts);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+ glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=yes
+else
+ glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+
+fi
+
+ if test $glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK = yes; then
+
+$as_echo "#define _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK 1" >>confdefs.h
+
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK" >&5
+$as_echo "$glibcxx_cv_PTHREAD_MUTEX_CLOCKLOCK" >&6; }
+
+ CXXFLAGS="$ac_save_CXXFLAGS"
+ LIBS="$ac_save_LIBS"
+ ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
ac_fn_c_check_header_mongrel "$LINENO" "locale.h" "ac_cv_header_locale_h" "$ac_includes_default"
if test "x$ac_cv_header_locale_h" = xyes; then :
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index ad4ae0c..35d346f 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -223,6 +223,9 @@ GLIBCXX_CHECK_TMPNAM
# For pthread_cond_clockwait
GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT
+# For pthread_mutex_clocklock
+GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK
+
AC_LC_MESSAGES
# For hardware_concurrency
diff --git a/libstdc++-v3/include/std/mutex b/libstdc++-v3/include/std/mutex
index 981b672..e06d286 100644
--- a/libstdc++-v3/include/std/mutex
+++ b/libstdc++-v3/include/std/mutex
@@ -134,22 +134,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
class __timed_mutex_impl
{
protected:
- typedef chrono::high_resolution_clock __clock_t;
-
template<typename _Rep, typename _Period>
bool
_M_try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{
- using chrono::steady_clock;
- auto __rt = chrono::duration_cast<steady_clock::duration>(__rtime);
- if (ratio_greater<steady_clock::period, _Period>())
+#if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
+ using __clock = chrono::steady_clock;
+#else
+ using __clock = chrono::system_clock;
+#endif
+
+ auto __rt = chrono::duration_cast<__clock::duration>(__rtime);
+ if (ratio_greater<__clock::period, _Period>())
++__rt;
- return _M_try_lock_until(steady_clock::now() + __rt);
+ return _M_try_lock_until(__clock::now() + __rt);
}
template<typename _Duration>
bool
- _M_try_lock_until(const chrono::time_point<__clock_t,
+ _M_try_lock_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
@@ -163,12 +166,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return static_cast<_Derived*>(this)->_M_timedlock(__ts);
}
+#ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
+ template<typename _Duration>
+ bool
+ _M_try_lock_until(const chrono::time_point<chrono::steady_clock,
+ _Duration>& __atime)
+ {
+ auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
+ auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
+
+ __gthread_time_t __ts = {
+ static_cast<std::time_t>(__s.time_since_epoch().count()),
+ static_cast<long>(__ns.count())
+ };
+
+ return static_cast<_Derived*>(this)->_M_clocklock(CLOCK_MONOTONIC,
+ __ts);
+ }
+#endif
+
template<typename _Clock, typename _Duration>
bool
_M_try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{
auto __rtime = __atime - _Clock::now();
- return _M_try_lock_until(__clock_t::now() + __rtime);
+ return _M_try_lock_for(__rtime);
}
};
@@ -229,6 +251,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
bool
_M_timedlock(const __gthread_time_t& __ts)
{ return !__gthread_mutex_timedlock(&_M_mutex, &__ts); }
+#if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
+ bool
+ _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts)
+ { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); }
+#endif
};
/// recursive_timed_mutex
@@ -289,6 +316,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
bool
_M_timedlock(const __gthread_time_t& __ts)
{ return !__gthread_recursive_mutex_timedlock(&_M_mutex, &__ts); }
+
+#ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
+ bool
+ _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts)
+ { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); }
+#endif
};
#else // !_GTHREAD_USE_MUTEX_TIMEDLOCK
--
git-series 0.9.1
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