cyb70289 commented on a change in pull request #12358:
URL: https://github.com/apache/arrow/pull/12358#discussion_r801345933
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File path: cpp/src/arrow/util/thread_pool.h
##########
@@ -373,7 +377,7 @@ class ARROW_EXPORT ThreadPool : public Executor {
State* state_;
bool shutdown_on_destroy_;
#ifndef _WIN32
- pid_t pid_;
+ std::atomic<pid_t> pid_;
Review comment:
Agreed the code should be safe in practice.
But at least in theory, I think it still violates data race free rule.
E.g., TSAN will complain below code.
```
#include <mutex>
#include <thread>
std::mutex g_mtx;
int g_i = 0;
void f() {
if (g_i == 0) {
std::lock_guard<std::mutex> lk(g_mtx);
if (g_i == 0) {
g_i = 1;
}
}
}
int main(void) {
std::thread t1(f), t2(f), t3(f), t4(f);
t1.join(); t2.join(); t3.join(); t4.join();
return 0;
}
```
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