MJIT: Do not hang after forking with threads

First, rb_mjit_fork should call rb_thread_atfork to stop threads after
fork in the child process. Unfortunately, we cannot use rb_fork_ruby to
prevent this kind of mistakes because MJIT needs special handling of
waiting_pid and mjit_pause/resume.

Second, mjit_waitpid_finished should be checked regardless of
trap_interrupt. It doesn't seem like the flag is not set when SIGCHLD is
handled for an MJIT child process.

1 files changed, 1 insertions, 0 deletions

diff --git a/process.c b/process.c
index 405c7edcb3..4465b36c51 100644
--- a/process.c
+++ b/process.c
@@ -4222,6 +4222,7 @@ rb_mjit_fork(void)
 
     after_fork_ruby();
     disable_child_handler_fork_parent(&old);
+    if (pid == 0) rb_thread_atfork();
 
     return pid;
 }