std::atomic bool or Normal global bool is good in single thread?
I have global vaiable in a below thread (bool allow) which restrict client to wait (by assign allow=false) till it is completed. After completed allow =true
bool allow =true;
static void * mythread(void *arg)
{
/* here is Lock mutex code */
allow =false;(**non atomic**)
system(command);
allow =true;
/* here is Unlock Mutex code */
}
if(allow)
{
// validate thread output
}
else
{
// wait
}
My concern is should i use std::atomic for the global varibale or its good as bove
std::atomic<bool>allow(true);
static void * mythread(void *arg)
{
/* here is Lock mutex code */
allow.store(false, std::memory_order_seq_cst);
system(command);
allow.store(true, std::memory_order_seq_cst);
/* here is Unlock Mutex code */
}
if(allow)
{
// validate thread output
}
else
{
// wait
}
If all access to the boolean is protected by a mutex, then it does not matter either way (in terms of correctness). Use the atomic<> or don't. The correctness of your code will not suffer.
But the performance might suffer, other than the fact that you are locking access to something that already has a mutex protecting it, std::atomic<> has the potential to use a mutex under the hood itself. std::atomic_flag however, is guaranteed to be lock-free. See the cppreference documentation for more.
If you have a single thread accessing that boolean, then no point having any synchronization at all.
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