From e2fe0aae43fee4815c1fc0896a2f03de35bfd873 Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Fri, 12 Dec 2025 22:12:41 +1300
Subject: [PATCH] Avoid race condition in
 `test_without_handle_interrupt_signal_works`. (#15504)

---
 ext/-test-/scheduler/scheduler.c                    | 13 ++++++++-----
 .../scheduler/test_interrupt_with_scheduler.rb      |  9 +++------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/ext/-test-/scheduler/scheduler.c b/ext/-test-/scheduler/scheduler.c
index f3badceb92..f8384f597e 100644
--- a/ext/-test-/scheduler/scheduler.c
+++ b/ext/-test-/scheduler/scheduler.c
@@ -1,5 +1,6 @@
 #include "ruby/ruby.h"
 #include "ruby/thread.h"
+#include "ruby/io.h"
 #include "ruby/fiber/scheduler.h"
 
 /*
@@ -24,6 +25,7 @@
  */
 
 struct blocking_state {
+    int notify_descriptor;
     volatile int interrupted;
 };
 
@@ -39,14 +41,14 @@ blocking_operation(void *argument)
 {
     struct blocking_state *blocking_state = (struct blocking_state *)argument;
 
-    while (true) {
-        struct timeval tv = {1, 0};  // 1 second timeout.
+    write(blocking_state->notify_descriptor, "x", 1);
 
+    while (!blocking_state->interrupted) {
+        struct timeval tv = {1, 0};  // 1 second timeout.
         int result = select(0, NULL, NULL, NULL, &tv);
 
         if (result == -1 && errno == EINTR) {
             blocking_state->interrupted = 1;
-            return NULL;
         }
 
         // Otherwise, timeout -> loop again.
@@ -56,9 +58,10 @@ blocking_operation(void *argument)
 }
 
 static VALUE
-scheduler_blocking_loop(VALUE self)
+scheduler_blocking_loop(VALUE self, VALUE notify)
 {
     struct blocking_state blocking_state = {
+        .notify_descriptor = rb_io_descriptor(notify),
         .interrupted = 0,
     };
 
@@ -84,5 +87,5 @@ Init_scheduler(void)
     VALUE mBug = rb_define_module("Bug");
     VALUE mScheduler = rb_define_module_under(mBug, "Scheduler");
 
-    rb_define_module_function(mScheduler, "blocking_loop", scheduler_blocking_loop, 0);
+    rb_define_module_function(mScheduler, "blocking_loop", scheduler_blocking_loop, 1);
 }
diff --git a/test/-ext-/scheduler/test_interrupt_with_scheduler.rb b/test/-ext-/scheduler/test_interrupt_with_scheduler.rb
index 42a109b98b..eb7a0647e5 100644
--- a/test/-ext-/scheduler/test_interrupt_with_scheduler.rb
+++ b/test/-ext-/scheduler/test_interrupt_with_scheduler.rb
@@ -26,23 +26,20 @@ class TestSchedulerInterruptHandling < Test::Unit::TestCase
           # Yield to the scheduler:
           sleep(0)
 
-          output.puts "ready"
-          Bug::Scheduler.blocking_loop
+          Bug::Scheduler.blocking_loop(output)
         end
       end
 
       output.close
-      assert_equal "ready\n", input.gets
+      assert_equal "x", input.read(1)
 
-      sleep 0.1 # Ensure the child is in the blocking loop
-      # $stderr.puts "Sending interrupt"
       Process.kill(:INT, pid)
 
       reaper = Thread.new do
         Process.waitpid2(pid)
       end
 
-      unless reaper.join(1)
+      unless reaper.join(10)
         Process.kill(:KILL, pid)
       end