volatile global x = 0;
reader() {
while (x == 0) {}
print ("World\n");
}
writer() {
print ("Hello, ")
x = 1;
}
thread (reader);
thread (writer);
https://en.wikipedia.org/wiki/Race_condition#:~:text=Data%20race%5Bedit,only%20atomic%20operations.
From wikipedia,
The precise definition of data race is specific to the formal concurrency model being used, but typically it refers to a situation where a memory operation in one thread could potentially attempt to access a memory location at the same time that a memory operation in another thread is writing to that memory location, in a context where this is dangerous.
- There are at least one thread that writes to x. (writer)
- There are at least one thread that reads to x. (reader)
- There is not any synchronization mechanism for accessing x. (Both of two threads access x without any locks.)
Therefore, I think the code above is data race. (Obviously not a race condition) Am i right?
Then what is the meaning of data race when a code is data race, but it generates the expected output? (We will see "Hello, World\n", assuming processor guarantees that a store to an address becomes visible for all load instructions issued after the store instruction)
----------- added working cpp code ------------
#include <iostream>
#include <thread>
volatile int x = 0;
void reader() {
while (x == 0 ) {}
std::cout << "World" << std::endl;
}
void writer() {
std::cout << "Hello, ";
x = 1;
}
int main() {
std::thread t1(reader);
std::thread t2(writer);
t2.join();
t1.join();
return 0;
}
