Fix race condition in signal handler query (#13712)

* Fix race condition in signal handler query

* Initialize signal lock dynamically and reset after fork

* Fix signal handler mutex initialization conditions

1 files changed, 1 insertions, 0 deletions

diff --git a/thread.c b/thread.c
index feb4419726..8442a7e786 100644
--- a/thread.c
+++ b/thread.c
@@ -4933,6 +4933,7 @@ rb_thread_atfork_internal(rb_thread_t *th, void (*atfork)(rb_thread_t *, const r
 
     thread_sched_atfork(TH_SCHED(th));
     ubf_list_atfork();
+    rb_signal_atfork();
 
     // OK. Only this thread accesses:
     ccan_list_for_each(&vm->ractor.set, r, vmlr_node) {