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.
* libstdc++-v3/acinclude.m4: Define
GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK to check for the presence of
both pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock.
* config.h.in: Add _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK define.
* configure.ac: Call GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK.
* configure: Add generated part to detect
pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
functions.
* include/std/shared_mutex (shared_timed_mutex): Define __clock_t
as the best clock to use for relative waits. (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. (try_lock_shared_until): Likewise.
---
libstdc++-v3/acinclude.m4 | 33 +++++++++++-
libstdc++-v3/config.h.in | 4 +-
libstdc++-v3/configure | 88 ++++++++++++++++++++++++++++-
libstdc++-v3/configure.ac | 3 +-
libstdc++-v3/include/std/shared_mutex | 87 ++++++++++++++++++++++------
5 files changed, 198 insertions(+), 17 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 9ecfa96..d860dbe 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4259,6 +4259,39 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK], [
])
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_RWLOCK_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_rwlock_clockrdlock, pthread_wlock_clockwrlock])
+ AC_CACHE_VAL(glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK, [
+ GCC_TRY_COMPILE_OR_LINK(
+ [#include <pthread.h>],
+ [pthread_rwlock_t rwl; struct timespec ts;]
+ [int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);]
+ [int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);],
+ [glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes],
+ [glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=no])
+ ])
+ if test $glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK = yes; then
+ AC_DEFINE(_GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK, 1, [Define if
pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock are available in
<pthread.h>.])
+ fi
+ AC_MSG_RESULT($glibcxx_cv_PTHREAD_RWLOCK_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 3d51534..8940e0c 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -1005,6 +1005,10 @@
/* Define if pthread_mutex_clocklock is available in <pthread.h>. */
#undef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
+/* Define if pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock are
+ available in <pthread.h>. */
+#undef _GLIBCXX_USE_PTHREAD_RWLOCK_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 bf0f50a..edb565f 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -21963,6 +21963,94 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
+# For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
+
+
+
+ ac_ext=cpp
+ac_cpp='$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_rwlock_clockrdlock, pthread_wlock_clockwrlock" >&5
+$as_echo_n "checking for pthread_rwlock_clockrdlock,
pthread_wlock_clockwrlock... " >&6; }
+ if ${glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+
+ if test x$gcc_no_link = xyes; then
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <pthread.h>
+int
+main ()
+{
+pthread_rwlock_t rwl; struct timespec ts;
+ int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);
+ int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes
+else
+ glibcxx_cv_PTHREAD_RWLOCK_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.$ac_ext
+/* end confdefs.h. */
+#include <pthread.h>
+int
+main ()
+{
+pthread_rwlock_t rwl; struct timespec ts;
+ int n = pthread_rwlock_clockrdlock(&rwl, CLOCK_REALTIME, &ts);
+ int m = pthread_rwlock_clockwrlock(&rwl, CLOCK_REALTIME, &ts);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+ glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=yes
+else
+ glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+
+fi
+
+ if test $glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK = yes; then
+
+$as_echo "#define _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK 1" >>confdefs.h
+
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result:
$glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK" >&5
+$as_echo "$glibcxx_cv_PTHREAD_RWLOCK_CLOCKLOCK" >&6; }
+
+ CXXFLAGS="$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 c1ecc67..699e55f 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -228,6 +228,9 @@ GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT
# For pthread_mutex_clocklock
GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK
+# For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
+GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK
+
AC_LC_MESSAGES
# For hardware_concurrency
diff --git a/libstdc++-v3/include/std/shared_mutex
b/libstdc++-v3/include/std/shared_mutex
index ffd93fb..b637bdc 100644
--- a/libstdc++-v3/include/std/shared_mutex
+++ b/libstdc++-v3/include/std/shared_mutex
@@ -450,7 +450,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using _Base = __shared_timed_mutex_base;
// Must use the same clock as condition_variable for __shared_mutex_cv.
- typedef chrono::system_clock __clock_t;
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ using __clock_t = chrono::steady_clock;
+#else
+ using __clock_t = chrono::system_clock;
+#endif
public:
shared_timed_mutex() = default;
@@ -491,7 +495,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Duration>
bool
- try_lock_until(const chrono::time_point<__clock_t, _Duration>& __atime)
+ try_lock_until(const chrono::time_point<chrono::system_clock,
+ _Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
@@ -512,23 +517,47 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return true;
}
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ template<typename _Duration>
+ bool
+ 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())
+ };
+
+ int __ret = pthread_rwlock_clockwrlock(&_M_rwlock, CLOCK_MONOTONIC,
+ &__ts);
+ // On self-deadlock, we just fail to acquire the lock. Technically,
+ // the program violated the precondition.
+ if (__ret == ETIMEDOUT || __ret == EDEADLK)
+ return false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ return true;
+ }
+#endif
+
template<typename _Clock, typename _Duration>
bool
- try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
+ try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{
- // DR 887 - Sync unknown clock to known clock.
- const typename _Clock::time_point __c_entry = _Clock::now();
- const __clock_t::time_point __s_entry = __clock_t::now();
- const auto __delta = __abs_time - __c_entry;
- const auto __s_atime = __s_entry + __delta;
- return try_lock_until(__s_atime);
+ typename _Clock::time_point __now = _Clock::now();
+ auto __rtime = __atime - __now;
+ return try_lock_for(__rtime);
}
// Shared ownership
template<typename _Duration>
bool
- try_lock_shared_until(const chrono::time_point<__clock_t,
+ try_lock_shared_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
@@ -564,17 +593,41 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return true;
}
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ template<typename _Duration>
+ bool
+ try_lock_shared_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())
+ };
+
+ int __ret = pthread_rwlock_clockrdlock(&_M_rwlock, CLOCK_MONOTONIC,
+ &__ts);
+ // On self-deadlock, we just fail to acquire the lock. Technically,
+ // the program violated the precondition.
+ if (__ret == ETIMEDOUT || __ret == EDEADLK)
+ return false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ return true;
+ }
+#endif
+
template<typename _Clock, typename _Duration>
bool
try_lock_shared_until(const chrono::time_point<_Clock,
- _Duration>& __abs_time)
+ _Duration>& __atime)
{
- // DR 887 - Sync unknown clock to known clock.
- const typename _Clock::time_point __c_entry = _Clock::now();
- const __clock_t::time_point __s_entry = __clock_t::now();
- const auto __delta = __abs_time - __c_entry;
- const auto __s_atime = __s_entry + __delta;
- return try_lock_shared_until(__s_atime);
+ typename _Clock::time_point __now = _Clock::now();
+ auto __rtime = __atime - __now;
+ return try_lock_shared_for(__rtime);
}
#else // ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
--
git-series 0.9.1
