我可以使用 std::stop_source 从工作线程中延迟取消所有工作线程吗？

Question

I have two threads running in parallell started from the main thread. Either thread may fail. If it do so I want to ask the other thread to cancel as well. In C++ 20 there is std::stop_token and std::stop_source . I have found several examples where the main thread ask all threads to cancel (deferred cancelation). However I have not found any examples where either worker thread may deferred cancel all other worker threads. How is this done?

Answer 1

In order for a location of code to be able to request a stop, that location must have a std::stop_source . In order for a location of code to be able to respond to the stop, it must have a std::stop_token taken from a particular stop_source .

Therefore, in order for a location of code to be able to both request and respond to a stop, it must have both the stop_source and the stop_token .

Now, since stop_source s are able to generate stop_token s, there's no reason why you can't just give the thread function a stop_source and have it extract a token from it. Of course, this won't be able to use std::jthread s convenience ability to detect that a thread function whose first argument is a stop_token and generate a stop_source , but the nature of your stopping needs wouldn't make that viable anyway.

Also, remember that stop_source is copyable ; the copies all share the same internal stop-state (along with any stop_token s created from them). So there's no reason to pass them by reference.