Revert SIGCHLD changes to diagnose CI failures. (#7517)

* Revert "Remove special handling of `SIGCHLD`. (#7482)"

This reverts commit 44a0711eab7fbc71ac2c8ff489d8c53e97a8fe75.

* Revert "Remove prototypes for functions that are no longer used. (#7497)"

This reverts commit 4dce12bead3bfd91fd80b5e7195f7f540ffffacb.

* Revert "Remove SIGCHLD `waidpid`. (#7476)"

This reverts commit 1658e7d96696a656d9bd0a0c84c82cde86914ba2.

* Fix change to rjit variable name.

1 files changed, 2 insertions, 0 deletions

diff --git a/thread_pthread.c b/thread_pthread.c
index c523509b9f..9723a5f6b4 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -348,6 +348,7 @@ do_gvl_timer(struct rb_thread_sched *sched, rb_thread_t *th)
     sched->timer_err = native_cond_timedwait(&th->nt->cond.readyq, &sched->lock, &abs);
 
     ubf_wakeup_all_threads();
+    ruby_sigchld_handler(vm);
 
     if (UNLIKELY(rb_signal_buff_size())) {
         if (th == vm->ractor.main_thread) {
@@ -2358,6 +2359,7 @@ native_sleep(rb_thread_t *th, rb_hrtime_t *rel)
         THREAD_BLOCKING_END(th);
 
         rb_sigwait_fd_put(th, sigwait_fd);
+        rb_sigwait_fd_migrate(th->vm);
     }
     else if (th == th->vm->ractor.main_thread) { /* always able to handle signals */
         native_ppoll_sleep(th, rel);