Crash when calling interrupt() on a boost::thread, which has another boost::thread

[elsamuko]

Hi there,

I'm getting a crash when calling interrupt() on an outer boost::thread, which runs an inner boost::thread, which is connected to a thread_guard. It's not crashing when calling join() manually on the inner thread.

Crash:
terminate called after throwing an instance of 'boost::thread_interrupted'

Source:
https://gist.github.com/elsamuko/6e178c37fa2cf8742cb6bf512f2ff866

Compile & Run:
http://coliru.stacked-crooked.com/a/46c512bf9a385fff

I'm running on Ubuntu 18.04. with g++ 7.5.0 and got the latest boost 1.78.0.

Let me know, if you need more information. Regards, Samuel

[sehe]

From my answer here:

You're mixing std::thread and boost::thread.

Only boost::thread knows about interruption points. Use that to fix:

Live On Coliru

    #include <iostream>
    #include <thread>

    #include <boost/thread.hpp>
    #include <boost/thread/thread_guard.hpp>

    void double_interrupt() {
        boost::thread outer([] {
            boost::thread inner([] {
                while (true) {
                    boost::this_thread::sleep_for(boost::chrono::milliseconds(1));
                }
            });
            {
                boost::this_thread::sleep_for(boost::chrono::milliseconds(1));
                std::cout << "Interrupting inner" << std::endl;
                boost::thread_guard<boost::join_if_joinable> guard(inner);
            }
        });
        std::cout << "Interrupting outer" << std::endl;
        outer.interrupt();
        outer.join();
    }
    int main() {
        std::cout << "Start" << std::endl;
        double_interrupt();
        std::cout << "End" << std::endl;
    }

Prints

Start
Interrupting outer
End

[elsamuko]

@sehe boost::sleep() is an interruption_point, which I don't want in the inner loop. Imagine it as some work is done here.

If you remove the sleep, it crashes again.

[sehe]

I'll continue the interaction at https://stackoverflow.com/a/71486609/85371 to prevent duplication.

[elsamuko]

I got a solution. It doesn't crash when using the thread_guard with a custom struct non_interruptable_interrupt_and_join_if_joinable:

    // helper struct to interrupt a boost::thread within a boost::thread
    struct non_interruptable_interrupt_and_join_if_joinable {
        template <class Thread>
        void operator()(Thread& t) {
            if(t.joinable()) {
                boost::this_thread::disable_interruption di;
                t.interrupt();
                t.join();
            }
        }
    };

[pdimov]

Should be fixed with https://github.com/boostorg/thread/commit/f71e0f1645413c3291e37d766e5b04bc57c6e132 and https://github.com/boostorg/thread/commit/8db325363b8e91de23c062ec8964bb605ad89f11.