上述代码中,use_x中assert(a.load(std::memory_order_relaxed)==99) 可能触发断言。 原因为: x通过std::memory_order_consume所得,由data dependency介绍部分知,操作p.store(x, std::memory_order_release) dependency-ordered-before 语句while (!(x = p.load(std::memory_order_consume))),而该语句又ca...
它通过使用标记memory_order_consume的原子操作引入,这是memory_order_acquire的一种特例,它限制了对直接依赖的数据同步。 这种内存顺序的一个重要用途,是在原子操作载入指向某数据的指针的场合。 通过在载入上使用memory_order_consume以及在之前的存储上使用memory_order_release,你可以确保所执行的数据得到正确的同步,...
memory_order_acquire:All writes in other threads that release the same atomic variable are visible in the current thread 初步理解为memory_order_consume会比memory_order_acquire少一些强制依赖关系,或者理解为memory_order_acquire的效果是释放操作后有内存栅设置。 gcc的解释更清晰一些: __ATOMIC_RELAXED No ...
data = 42; ptr.store(p, std::memory_order_release); } voidconsumer() { std::string* p2; while(!(p2 = ptr.load(std::memory_order_consume))) ; assert(*p2 =="Hello");// never fires: *p2 carries dependency from ptr assert(data == 42);// may or may not fire: data does not...
atoData.store(2014,std::memory_order_relaxed); ptr.store(p, std::memory_order_release); }voidconsumer(){ std::string* p2;while(!(p2 = ptr.load(std::memory_order_consume))); std::cout <<"*p2: "<< *p2 << std::endl;
auto q = p.load(std::memory_order_consume); return *q + prefetch2; } The value ofv2is not dependent on what was loaded fromp. Therefore, the compiler and processor are permitted to advance the fetch ofv2ahead of the load ofp. Note that anacquireload ofpwould have prohibited this reo...
load(std::memory_order::consume); // not acquire // assume this is done smartly in a loop that checks for null, and exchanges in `null`. } } (or equivalent C18 code).Activity Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment...
- [The Purpose of memory_order_consume in C++11](http://preshing.com/20140709/the-purpose-of-memory_order_consume-in-cpp11/) - [(抄訳)N4215 `memory_order_consume`の利用と実装に向けて[§5-6のみ]](http://d.hatena.ne.jp/yohhoy/20141115/p1) 0 comments on commit c84f565 Please ...
memory_order_acq_rel, memory_order_seq_cst }; The above values are referred to asmemory ordering constraints. Each of them has its intended purpose. Among them,memory_order_consumeis probably the least well-understood. It’s the most complicated ordering constraint, and it offers the least re...
Without memory order consume, both the compiler and (again, in the case of DEC Alpha) the CPU would be within their rights to carry out aggres- sive data-speculation optimizations that would per- mit readers to see pre-initialization values in the newly added data elements. The purpose of ...