返回原始值的操作:atomic_fetch_{} () 交换操作(swap operations):xchg(), cmpxchg() and try_cmpxchg() 杂项misc:在给定接口的情况下,通常使用 (try_)cmpxchg 循环来实现常用的特殊用途操作,但这些操作是时间关键的,并且可以(通常)在LL/SC体系结构上更有效地实现。 所有这些操作都是SMP-atomic;也就是说,操...
atomic_try_cmpxchg{,_relaxed,_acquire,_release}() Reference count 引用计数: atomic_add_unless(), atomic_inc_not_zero() atomic_sub_and_test(), atomic_dec_and_test() Misc 杂项: atomic_inc_and_test(), atomic_add_negative() atomic_dec_unless_positive(), atomic_inc_unless_negative() Barr...
arch_try_cmpxchg64_release(__ai_ptr, __ai_oldp, __VA_ARGS__); \ }) #define try_cmpxchg64_relaxed(ptr, oldp, ...) \ ({ \ typeof(ptr) __ai_ptr = (ptr); \ typeof(oldp) __ai_oldp = (oldp); \ instrument_atomic_write(__ai_ptr, sizeof(*__ai_ptr)); \ instrument...
static if (T.sizeof > size_t.sizeof) { version (X86) { // cmpxchg8b only requires 4-bytes alignment return cast(size_t)ptr % size_t.sizeof == 0; } else { // e.g., x86_64 cmpxchg16b requires 16-bytes alignment return cast(size_t)ptr % T.sizeof == 0; } } else { ...
have better CAS and CMPXCHG performance, a conclusion again largely supported by the data. The db benchmark is an exception, where the largest gain was seen on an older UltraSPARC III system; we believe this may be related to relatively poor associativity of the data cache on this chip. ...
11 @@ #include <cassert> #include <cmpxchg_loop.h> +#include "atomic_helpers.h" template <class T> -void -test() -{ +struct TestFn { + void operator()() const { { typedef std::atomic<T> A; A a; @@ -54,37 +54,10 @@ assert(a == T(2)); assert(t == T(2)); }...
We got lucky. The compiler was clever enough to see thatTermsfits inside a single 64-bit register, and implementedcompare_exchange_weakusinglock cmpxchg. The compiled code is lock-free. This brings up an interesting point: In general, the C++11 standard doesnotguarantee that atomic operations ...
This would be generally followed by a LOCK CMPXCHG to attempt to get the mutex. Failure to obtain the mutex (in a well coded routine) results in a branch to a retry location and thus re-enabling the interrupts. If the mutex is obtained the code falls through thus con...
10 @@ #include <cassert> #include <cmpxchg_loop.h> +#include "atomic_helpers.h" template <class T> -void -test() +void test() { { typedef std::atomic<T> A; @@ -56,35 +56,7 @@ } } -struct A -{ - int i; - - explicit A(int d = 0) noexcept {i=d;} - - friend...
This would be generally followed by a LOCK CMPXCHG to attempt to get the mutex. Failure to obtain the mutex (in a well coded routine) results in a branch to a retry location and thus re-enabling the interrupts. If the mutex is obtained the code falls through thus con...