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Fix a typo in __gthr_win32_abs_to_rel_time that caused it to return a
relative time in seconds instead of milliseconds. As a consequence,
__gthr_win32_cond_timedwait called SleepConditionVariableCS with a
1000x shorter timeout; this caused ~1000x more spurious wakeups in
CV timed waits such as std::condition_variable::wait_for or wait_until,
resulting generally in much higher CPU usage.
This can be demonstrated by this sample program:
```
int main() {
std::condition_variable cv;
std::mutex mx;
bool pass = false;
auto thread_fn = [&](bool timed) {
int wakeups = 0;
using sc = std::chrono::system_clock;
auto before = sc::now();
std::unique_lock<std::mutex> ml(mx);
if (timed) {
cv.wait_for(ml, std::chrono::seconds(2), [&]{
++wakeups;
return pass;
});
} else {
cv.wait(ml, [&]{
++wakeups;
return pass;
});
}
printf("pass: %d; wakeups: %d; elapsed: %d ms\n", pass, wakeups,
int((sc::now() - before) / std::chrono::milliseconds(1)));
pass = false;
};
{
// timed wait, let expire
std::thread t(thread_fn, true);
t.join();
}
{
// timed wait, wake up explicitly after 1 second
std::thread t(thread_fn, true);
std::this_thread::sleep_for(std::chrono::seconds(1));
{
std::unique_lock<std::mutex> ml(mx);
pass = true;
}
cv.notify_all();
t.join();
}
{
// non-timed wait, wake up explicitly after 1 second
std::thread t(thread_fn, false);
std::this_thread::sleep_for(std::chrono::seconds(1));
{
std::unique_lock<std::mutex> ml(mx);
pass = true;
}
cv.notify_all();
t.join();
}
return 0;
}
```
On builds based on non-affected threading models (e.g. POSIX on Linux,
or winpthreads or MCF on Win32) the output is something like
```
pass: 0; wakeups: 2; elapsed: 2000 ms
pass: 1; wakeups: 2; elapsed: 991 ms
pass: 1; wakeups: 2; elapsed: 996 ms
```
while with the Win32 threading model we get
```
pass: 0; wakeups: 1418; elapsed: 2000 ms
pass: 1; wakeups: 479; elapsed: 988 ms
pass: 1; wakeups: 2; elapsed: 992 ms
```
(notice the huge number of wakeups in the timed wait cases only).
This commit fixes the conversion, adjusting the final division by
NSEC100_PER_SEC to use NSEC100_PER_MSEC instead (already defined in the
file and not used in any other place, so probably just a typo).
libgcc/ChangeLog:
PR libgcc/113850
* config/i386/gthr-win32-cond.c (__gthr_win32_abs_to_rel_time):
fix absolute timespec to relative milliseconds count
conversion (it incorrectly returned seconds instead of
milliseconds); this avoids spurious wakeups in
__gthr_win32_cond_timedwait
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This reimplements the GNU threads library on native Windows (except for the
Objective-C specific subset) using direct Win32 API calls, in lieu of the
implementation based on semaphores. This base implementations requires
Windows XP/Server 2003, which was the default minimal setting of MinGW-W64
until end of 2020. This also adds the support required for the C++11 threads,
using again direct Win32 API calls; this additional layer requires Windows
Vista/Server 2008 and is enabled only if _WIN32_WINNT >= 0x0600.
This also changes libstdc++ to pass -D_WIN32_WINNT=0x0600 but only when the
switch --enable-libstdcxx-threads is passed, which means that C++11 threads
are still disabled by default *unless* MinGW-W64 itself is configured for
Windows Vista/Server 2008 or later by default (this has been the case in
the development version since end of 2020, for earlier versions you can
configure it --with-default-win32-winnt=0x0600 to get the same effect).
I only manually tested it on i686-w64-mingw32 and x86_64-w64-mingw32 but
AdaCore has used it in their C/C++/Ada compilers for 3 years now and the
30_threads chapter of the libstdc++ testsuite was clean at the time.
2022-10-31 Eric Botcazou <ebotcazou@adacore.com>
libgcc/
* config.host (i[34567]86-*-mingw*): Add thread fragment after EH one
as well as new i386/t-slibgcc-mingw fragment.
(x86_64-*-mingw*): Likewise.
* config/i386/gthr-win32.h: If _WIN32_WINNT is at least 0x0600, define
both __GTHREAD_HAS_COND and __GTHREADS_CXX0X to 1.
Error out if _GTHREAD_USE_MUTEX_TIMEDLOCK is 1.
Include stdlib.h instead of errno.h and do not include _mingw.h.
(CONST_CAST2): Add specific definition for C++.
(ATTRIBUTE_UNUSED): New macro.
(__UNUSED_PARAM): Delete.
Define WIN32_LEAN_AND_MEAN before including windows.h.
(__gthread_objc_data_tls): Use TLS_OUT_OF_INDEXES instead of (DWORD)-1.
(__gthread_objc_init_thread_system): Likewise.
(__gthread_objc_thread_get_data): Minor tweak.
(__gthread_objc_condition_allocate): Use ATTRIBUTE_UNUSED.
(__gthread_objc_condition_deallocate): Likewise.
(__gthread_objc_condition_wait): Likewise.
(__gthread_objc_condition_broadcast): Likewise.
(__gthread_objc_condition_signal): Likewise.
Include sys/time.h.
(__gthr_win32_DWORD): New typedef.
(__gthr_win32_HANDLE): Likewise.
(__gthr_win32_CRITICAL_SECTION): Likewise.
(__gthr_win32_CONDITION_VARIABLE): Likewise.
(__gthread_t): Adjust.
(__gthread_key_t): Likewise.
(__gthread_mutex_t): Likewise.
(__gthread_recursive_mutex_t): Likewise.
(__gthread_cond_t): New typedef.
(__gthread_time_t): Likewise.
(__GTHREAD_MUTEX_INIT_DEFAULT): Delete.
(__GTHREAD_RECURSIVE_MUTEX_INIT_DEFAULT): Likewise.
(__GTHREAD_COND_INIT_FUNCTION): Define.
(__GTHREAD_TIME_INIT): Likewise.
(__gthr_i486_lock_cmp_xchg): Delete.
(__gthr_win32_create): Declare.
(__gthr_win32_join): Likewise.
(__gthr_win32_self): Likewise.
(__gthr_win32_detach): Likewise.
(__gthr_win32_equal): Likewise.
(__gthr_win32_yield): Likewise.
(__gthr_win32_mutex_destroy): Likewise.
(__gthr_win32_cond_init_function): Likewise if __GTHREADS_HAS_COND is 1.
(__gthr_win32_cond_broadcast): Likewise.
(__gthr_win32_cond_signal): Likewise.
(__gthr_win32_cond_wait): Likewise.
(__gthr_win32_cond_timedwait): Likewise.
(__gthr_win32_recursive_mutex_init_function): Delete.
(__gthr_win32_recursive_mutex_lock): Likewise.
(__gthr_win32_recursive_mutex_unlock): Likewise.
(__gthr_win32_recursive_mutex_destroy): Likewise.
(__gthread_create): New inline function.
(__gthread_join): Likewise.
(__gthread_self): Likewise.
(__gthread_detach): Likewise.
(__gthread_equal): Likewise.
(__gthread_yield): Likewise.
(__gthread_cond_init_function): Likewise if __GTHREADS_HAS_COND is 1.
(__gthread_cond_broadcast): Likewise.
(__gthread_cond_signal): Likewise.
(__gthread_cond_wait): Likewise.
(__gthread_cond_timedwait): Likewise.
(__GTHREAD_WIN32_INLINE): New macro.
(__GTHREAD_WIN32_COND_INLINE): Likewise.
(__GTHREAD_WIN32_ACTIVE_P): Likewise.
Define WIN32_LEAN_AND_MEAN before including windows.h.
(__gthread_once): Minor tweaks.
(__gthread_key_create): Use ATTRIBUTE_UNUSED and TLS_OUT_OF_INDEXES.
(__gthread_key_delete): Minor tweak.
(__gthread_getspecific): Likewise.
(__gthread_setspecific): Likewise.
(__gthread_mutex_init_function): Reimplement.
(__gthread_mutex_destroy): Likewise.
(__gthread_mutex_lock): Likewise.
(__gthread_mutex_trylock): Likewise.
(__gthread_mutex_unlock): Likewise.
(__gthr_win32_abs_to_rel_time): Declare.
(__gthread_recursive_mutex_init_function): Reimplement.
(__gthread_recursive_mutex_destroy): Likewise.
(__gthread_recursive_mutex_lock): Likewise.
(__gthread_recursive_mutex_trylock): Likewise.
(__gthread_recursive_mutex_unlock): Likewise.
(__gthread_cond_destroy): New inline function.
(__gthread_cond_wait_recursive): Likewise.
* config/i386/gthr-win32.c: Delete everything.
Include gthr-win32.h to get the out-of-line version of inline routines.
Add compile-time checks for the local version of the Win32 types.
* config/i386/gthr-win32-cond.c: New file.
* config/i386/gthr-win32-thread.c: Likewise.
* config/i386/t-gthr-win32: Add config/i386/gthr-win32-thread.c to the
EH part, config/i386/gthr-win32-cond.c and config/i386/gthr-win32.c to
the static version of libgcc.
* config/i386/t-slibgcc-mingw: New file.
* config/i386/libgcc-mingw.ver: Likewise.
libstdc++-v3/
* acinclude.m4 (GLIBCXX_EXPORT_FLAGS): Substitute CPPFLAGS.
(GLIBCXX_ENABLE_LIBSTDCXX_TIME): Set ac_has_sched_yield and
ac_has_win32_sleep to yes for MinGW. Change HAVE_WIN32_SLEEP
into _GLIBCXX_USE_WIN32_SLEEP.
(GLIBCXX_CHECK_GTHREADS): Add _WIN32_THREADS to compilation flags for
Win32 threads and force _GTHREAD_USE_MUTEX_TIMEDLOCK to 0 for them.
Add -D_WIN32_WINNT=0x0600 to compilation flags if yes was configured
and add it to CPPFLAGS on success.
* config.h.in: Regenerate.
* configure: Likewise.
* config/os/mingw32-w64/os_defines.h (_GLIBCXX_USE_GET_NPROCS_WIN32):
Define to 1.
* config/os/mingw32/os_defines.h (_GLIBCXX_USE_GET_NPROCS_WIN32): Ditto
* src/c++11/thread.cc (get_nprocs): Provide Win32 implementation if
_GLIBCXX_USE_GET_NPROCS_WIN32 is defined. Replace HAVE_WIN32_SLEEP
with USE_WIN32_SLEEP.
* testsuite/19_diagnostics/headers/system_error/errc_std_c++0x.cc: Add
missing conditional compilation.
* testsuite/lib/libstdc++.exp (check_v3_target_sleep): Add support for
_GLIBCXX_USE_WIN32_SLEEP.
(check_v3_target_nprocs): Likewise for _GLIBCXX_USE_GET_NPROCS_WIN32.
Signed-off-by: Eric Botcazou <ebotcazou@adacore.com>
Signed-off-by: Jonathan Yong <10walls@gmail.com>
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