[3.3] Fix deadlock on th->interrupt_lock after fork

[Bug #21860]

If a thread was holding this lock before fork, it will not exist in the
child process. We should re-initialize these locks as we do with the VM
locks when forking.

Co-Authored-By: John Hawthorn <john@hawthorn.email>
Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>

3 files changed, 13 insertions, 2 deletions

diff --git a/bootstraptest/test_fork.rb b/bootstraptest/test_fork.rb
index 0cdfb5ab24..7a613026ad 100644
--- a/bootstraptest/test_fork.rb
+++ b/bootstraptest/test_fork.rb
@@ -88,14 +88,19 @@ assert_equal 'ok', %q{
 
   10.times do
     pid = fork{ exit!(0) }
-    deadline = now + 1
-    until Process.waitpid(pid, Process::WNOHANG)
+    deadline = now + 10
+    while true
+      _, status = Process.waitpid2(pid, Process::WNOHANG)
+      break if status
       if now > deadline
         Process.kill(:KILL, pid)
         raise "failed"
       end
       sleep 0.001
     end
+    unless status.success?
+      raise "child exited with status #{status}"
+    end
   rescue NotImplementedError
   end
   :ok
diff --git a/thread.c b/thread.c
index 1fe1e01595..b2b5177d4e 100644
--- a/thread.c
+++ b/thread.c
@@ -4698,6 +4698,7 @@ static void
 terminate_atfork_i(rb_thread_t *th, const rb_thread_t *current_th)
 {
     if (th != current_th) {
+        rb_native_mutex_initialize(&th->interrupt_lock);
         rb_mutex_abandon_keeping_mutexes(th);
         rb_mutex_abandon_locking_mutex(th);
         thread_cleanup_func(th, TRUE);
diff --git a/thread_pthread.c b/thread_pthread.c
index ed624416aa..77994796f1 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1531,6 +1531,11 @@ thread_sched_atfork(struct rb_thread_sched *sched)
     vm->ractor.sched.running_cnt = 0;
 
     rb_native_mutex_initialize(&vm->ractor.sched.lock);
+#if VM_CHECK_MODE > 0
+    vm->ractor.sched.lock_owner = NULL;
+    vm->ractor.sched.locked = false;
+#endif
+
     // rb_native_cond_destroy(&vm->ractor.sched.cond);
     rb_native_cond_initialize(&vm->ractor.sched.cond);
     rb_native_cond_initialize(&vm->ractor.sched.barrier_complete_cond);