[英]Allocating a atomic on shared memory
I am trying to allocate a atomic on a shared memory block (on linux). 我正在尝试在共享内存块上分配原子(在Linux上)。 The atomic will be accessed and modified my multiple threads simultaneously. 原子将被同时访问并修改我的多个线程。 The rational behind allocating it on shared memory is because I want to persist the values so if my process is restarted the previous state can be recovered. 在共享内存上分配它的原因是因为我想保留这些值,因此,如果我的进程重新启动,则可以恢复以前的状态。 I know for a fact if i use a mutex in shared memory i have to initialize it as a SHARED. 我知道一个事实,如果我在共享内存中使用互斥锁,则必须将其初始化为SHARED。 Is there any such requirement for atomics? 对原子有这样的要求吗? Is this feasible? 这可行吗?
Yes, you can do that. 是的,你可以这么做。 Here is an example I ripped from Quora ( ripped code from Quora ), not my code and includes boost so I have not tested it: 这是我从Quora 翻录的一个示例(从Quora 翻录的代码 ),而不是我的代码,包括boost,所以我没有对其进行测试:
#include <atomic>
#include <string>
#include <iostream>
#include <cstdlib>
#include <boost/interprocess/managed_shared_memory.hpp>
using namespace std::string_literals;
namespace bip = boost::interprocess;
static_assert(ATOMIC_INT_LOCK_FREE == 2,
"atomic_int must be lock-free");
int main(int argc, char *argv[])
{
if(argc == 1) //Parent process
{
struct shm_remove {
shm_remove() { bip::shared_memory_object::remove("szMem");}
~shm_remove(){ bip::shared_memory_object::remove("szMem");}
} remover;
bip::managed_shared_memory segment(bip::create_only,
"szMem", 65536);
auto ap = segment.construct<std::atomic_int>("the counter")(0);
//Launch 5 child processes
std::string s = argv[0] +" child"s;
std::system((s + '&' + s + '&' + s + '&' + s + '&' + s).c_str());
std::cout << "parent existing: counter = " << *ap << '\n';
segment.destroy<std::atomic_int>("the counter");
} else { // child
bip::managed_shared_memory segment(bip::open_only, "szMem");
auto res = segment.find<std::atomic_int>("the counter");
for(int n = 0; n < 100000; ++n)
++*res.first; // C++17 will remove the dumb "first"
std::cout << "child exiting, counter = " << *res.first << '\n';
}
}
Here is documentation: link to Boost docs 这里是文档: 链接到Boost docs
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