30 #ifndef _GLIBCXX_ATOMIC_WAIT_H 31 #define _GLIBCXX_ATOMIC_WAIT_H 1 33 #pragma GCC system_header 36 #if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX 38 #include <bits/gthr.h> 41 #ifdef _GLIBCXX_HAVE_LINUX_FUTEX 51 #define __cpp_lib_atomic_wait 201907L 53 namespace std _GLIBCXX_VISIBILITY(default)
55 _GLIBCXX_BEGIN_NAMESPACE_VERSION
58 #ifdef _GLIBCXX_HAVE_LINUX_FUTEX 59 using __platform_wait_t = int;
60 static constexpr
size_t __platform_wait_alignment = 4;
62 using __platform_wait_t = uint64_t;
63 static constexpr
size_t __platform_wait_alignment
64 = __alignof__(__platform_wait_t);
68 template<
typename _Tp>
69 inline constexpr
bool __platform_wait_uses_type
70 #ifdef _GLIBCXX_HAVE_PLATFORM_WAIT 72 && ((
sizeof(_Tp) ==
sizeof(__detail::__platform_wait_t))
73 && (
alignof(_Tp*) >= __platform_wait_alignment));
80 #ifdef _GLIBCXX_HAVE_LINUX_FUTEX 81 #define _GLIBCXX_HAVE_PLATFORM_WAIT 1 82 enum class __futex_wait_flags : int
84 #ifdef _GLIBCXX_HAVE_LINUX_FUTEX_PRIVATE 93 __wait_private = __wait | __private_flag,
94 __wake_private = __wake | __private_flag,
95 __wait_bitset_private = __wait_bitset | __private_flag,
96 __wake_bitset_private = __wake_bitset | __private_flag,
97 __bitset_match_any = -1
100 template<
typename _Tp>
102 __platform_wait(
const _Tp* __addr, __platform_wait_t __val) noexcept
104 auto __e = syscall (SYS_futex, static_cast<const void*>(__addr),
105 static_cast<int>(__futex_wait_flags::__wait_private),
107 if (!__e || errno == EAGAIN)
110 __throw_system_error(errno);
113 template<
typename _Tp>
115 __platform_notify(
const _Tp* __addr,
bool __all) noexcept
117 syscall (SYS_futex, static_cast<const void*>(__addr),
118 static_cast<int>(__futex_wait_flags::__wake_private),
119 __all ? INT_MAX : 1);
129 __thread_yield() noexcept
131 #if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD 137 __thread_relax() noexcept
139 #if defined __i386__ || defined __x86_64__ 140 __builtin_ia32_pause();
146 constexpr
auto __atomic_spin_count_1 = 12;
147 constexpr
auto __atomic_spin_count_2 = 4;
149 struct __default_spin_policy
152 operator()() const noexcept
156 template<
typename _Pred,
157 typename _Spin = __default_spin_policy>
159 __atomic_spin(_Pred& __pred, _Spin __spin = _Spin{ }) noexcept
161 for (
auto __i = 0; __i < __atomic_spin_count_1; ++__i)
165 __detail::__thread_relax();
168 for (
auto __i = 0; __i < __atomic_spin_count_2; ++__i)
172 __detail::__thread_yield();
184 template<
typename _Tp>
185 bool __atomic_compare(
const _Tp& __a,
const _Tp& __b)
188 return __builtin_memcmp(&__a, &__b,
sizeof(_Tp)) != 0;
191 struct __waiter_pool_base
193 #ifdef __cpp_lib_hardware_interference_size 194 static constexpr
auto _S_align = hardware_destructive_interference_size;
196 static constexpr
auto _S_align = 64;
199 alignas(_S_align) __platform_wait_t _M_wait = 0;
201 #ifndef _GLIBCXX_HAVE_PLATFORM_WAIT 205 alignas(_S_align) __platform_wait_t _M_ver = 0;
207 #ifndef _GLIBCXX_HAVE_PLATFORM_WAIT 210 __waiter_pool_base() =
default;
213 _M_enter_wait() noexcept
214 { __atomic_fetch_add(&_M_wait, 1, __ATOMIC_ACQ_REL); }
217 _M_leave_wait() noexcept
218 { __atomic_fetch_sub(&_M_wait, 1, __ATOMIC_ACQ_REL); }
221 _M_waiting() const noexcept
223 __platform_wait_t __res;
224 __atomic_load(&_M_wait, &__res, __ATOMIC_ACQUIRE);
229 _M_notify(
const __platform_wait_t* __addr,
bool __all,
bool __bare) noexcept
231 if (!(__bare || _M_waiting()))
234 #ifdef _GLIBCXX_HAVE_PLATFORM_WAIT 235 __platform_notify(__addr, __all);
244 static __waiter_pool_base&
245 _S_for(
const void* __addr) noexcept
247 constexpr uintptr_t __ct = 16;
248 static __waiter_pool_base __w[__ct];
249 auto __key = (uintptr_t(__addr) >> 2) % __ct;
254 struct __waiter_pool : __waiter_pool_base
257 _M_do_wait(
const __platform_wait_t* __addr, __platform_wait_t __old) noexcept
259 #ifdef _GLIBCXX_HAVE_PLATFORM_WAIT 260 __platform_wait(__addr, __old);
262 __platform_wait_t __val;
263 __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
266 lock_guard<mutex> __l(_M_mtx);
269 #endif // __GLIBCXX_HAVE_PLATFORM_WAIT 273 template<
typename _Tp>
276 using __waiter_type = _Tp;
279 __platform_wait_t* _M_addr;
281 template<
typename _Up>
282 static __platform_wait_t*
283 _S_wait_addr(
const _Up* __a, __platform_wait_t* __b)
285 if constexpr (__platform_wait_uses_type<_Up>)
286 return reinterpret_cast<__platform_wait_t*
>(
const_cast<_Up*
>(__a));
291 static __waiter_type&
292 _S_for(
const void* __addr) noexcept
294 static_assert(
sizeof(__waiter_type) ==
sizeof(__waiter_pool_base));
295 auto& res = __waiter_pool_base::_S_for(__addr);
296 return reinterpret_cast<__waiter_type&
>(res);
299 template<
typename _Up>
300 explicit __waiter_base(
const _Up* __addr) noexcept
301 : _M_w(_S_for(__addr))
302 , _M_addr(_S_wait_addr(__addr, &_M_w._M_ver))
307 _M_notify(
bool __all,
bool __bare =
false)
309 if (_M_addr == &_M_w._M_ver)
310 __atomic_fetch_add(_M_addr, 1, __ATOMIC_ACQ_REL);
311 _M_w._M_notify(_M_addr, __all, __bare);
314 template<
typename _Up,
typename _ValFn,
315 typename _Spin = __default_spin_policy>
317 _S_do_spin_v(__platform_wait_t* __addr,
318 const _Up& __old, _ValFn __vfn,
319 __platform_wait_t& __val,
320 _Spin __spin = _Spin{ })
322 auto const __pred = [=]
323 {
return __detail::__atomic_compare(__old, __vfn()); };
325 if constexpr (__platform_wait_uses_type<_Up>)
331 __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
333 return __atomic_spin(__pred, __spin);
336 template<
typename _Up,
typename _ValFn,
337 typename _Spin = __default_spin_policy>
339 _M_do_spin_v(
const _Up& __old, _ValFn __vfn,
340 __platform_wait_t& __val,
341 _Spin __spin = _Spin{ })
342 {
return _S_do_spin_v(_M_addr, __old, __vfn, __val, __spin); }
344 template<
typename _Pred,
345 typename _Spin = __default_spin_policy>
347 _S_do_spin(
const __platform_wait_t* __addr,
349 __platform_wait_t& __val,
350 _Spin __spin = _Spin{ })
352 __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
353 return __atomic_spin(__pred, __spin);
356 template<
typename _Pred,
357 typename _Spin = __default_spin_policy>
359 _M_do_spin(_Pred __pred, __platform_wait_t& __val,
360 _Spin __spin = _Spin{ })
361 {
return _S_do_spin(_M_addr, __pred, __val, __spin); }
364 template<
typename _EntersWait>
365 struct __waiter : __waiter_base<__waiter_pool>
367 using __base_type = __waiter_base<__waiter_pool>;
369 template<
typename _Tp>
370 explicit __waiter(
const _Tp* __addr) noexcept
371 : __base_type(__addr)
373 if constexpr (_EntersWait::value)
374 _M_w._M_enter_wait();
379 if constexpr (_EntersWait::value)
380 _M_w._M_leave_wait();
383 template<
typename _Tp,
typename _ValFn>
385 _M_do_wait_v(_Tp __old, _ValFn __vfn)
387 __platform_wait_t __val;
388 if (__base_type::_M_do_spin_v(__old, __vfn, __val))
390 __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
393 template<
typename _Pred>
395 _M_do_wait(_Pred __pred) noexcept
399 __platform_wait_t __val;
400 if (__base_type::_M_do_spin(__pred, __val))
402 __base_type::_M_w._M_do_wait(__base_type::_M_addr, __val);
408 using __enters_wait = __waiter<std::true_type>;
409 using __bare_wait = __waiter<std::false_type>;
412 template<
typename _Tp,
typename _ValFn>
414 __atomic_wait_address_v(
const _Tp* __addr, _Tp __old,
415 _ValFn __vfn) noexcept
417 __detail::__enters_wait __w(__addr);
418 __w._M_do_wait_v(__old, __vfn);
421 template<
typename _Tp,
typename _Pred>
423 __atomic_wait_address(
const _Tp* __addr, _Pred __pred) noexcept
425 __detail::__enters_wait __w(__addr);
426 __w._M_do_wait(__pred);
430 template<
typename _Pred>
432 __atomic_wait_address_bare(
const __detail::__platform_wait_t* __addr,
433 _Pred __pred) noexcept
435 #ifdef _GLIBCXX_HAVE_PLATFORM_WAIT 438 __detail::__platform_wait_t __val;
439 if (__detail::__bare_wait::_S_do_spin(__addr, __pred, __val))
441 __detail::__platform_wait(__addr, __val);
444 #else // !_GLIBCXX_HAVE_PLATFORM_WAIT 445 __detail::__bare_wait __w(__addr);
446 __w._M_do_wait(__pred);
450 template<
typename _Tp>
452 __atomic_notify_address(
const _Tp* __addr,
bool __all) noexcept
454 __detail::__bare_wait __w(__addr);
455 __w._M_notify(__all,
true);
460 __atomic_notify_address_bare(
const __detail::__platform_wait_t* __addr,
463 #ifdef _GLIBCXX_HAVE_PLATFORM_WAIT 464 __detail::__platform_notify(__addr, __all);
466 __detail::__bare_wait __w(__addr);
467 __w._M_notify(__all,
true);
470 _GLIBCXX_END_NAMESPACE_VERSION
472 #endif // GTHREADS || LINUX_FUTEX 473 #endif // _GLIBCXX_ATOMIC_WAIT_H
ISO C++ entities toplevel namespace is std.