[Linux] boost::process:: child ::wait_until is not thread-safe

[AlexeyZaharov]

Hi! I faced with the problem that my process hangs up while it uses wait_until() of child::process. So I watched boost code and find that boost::process:: child ::wait_until is not thread-safe

1. struct signal_interceptor_t is used for setting custom reaction on signal with using system ::signal. So handler_func is a new handler and sigchld_handler is setting for previous handler
2. The problem is that signal handler - atribut of the process, not thread, so if the next thread call ::signal then sigchld_handler is setting for handler_func
3. Which thread will be used for handle signal is undefined. So thread with sigchld_handler == handler_func can be used! And this cause infinite loop
4. You can face with the problem in this code, which uses problem part of wait_until. (On my system signals are handled by main thread). Also attach out of the programm
   bug_wait_until.cpp.txt
   out.txt

So can you update your documentation with this note please?

UPD: After I write this issue I found the same:
POSIX wait_for() crashes when multiple threads run it simultaneously
POSIX wait_for - stack overflow
child::wait_for() may block indefinitely

[klemens-morgenstern]

I deprecated them, they're generally unsafe.

[AlexeyZaharov]

Can you update documentation with information about deprecation please? I can`t find this info

[jens-diewald]

I, too, would appreciate information on the deprecation.
Specifically, on Windows, these functions are fine, right?
Do you plan to remove them in a future release?

[rroquetto-uptycs]

@klemens-morgenstern Following up on the previous comments, do you have any references on the rationale for the deprecation, so that I can better understand what the issue is and look for alternatives moving forward?
Thanks!

[klemens-morgenstern]

They are fine on windows, but unsafe on linux. Therefor process cant provide a portable function that is safe.

The recommendation is to use V2 and async_wait, so you can us an asio timer to create a timeout.

[rroquetto-uptycs]

Ah great, thank you very much for such a prompt response!