From 9af163c19e715200687a31330cf5ecc2b6ecf11a Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Fri, 6 Mar 2026 12:38:13 -0800
Subject: [PATCH] test_poll_blocking: Wait for worker threads to start before
 sleeping.

This means that even if the threads take a while to start they should
still block for at least TIMEOUT_MS in poll/select.
---
 test/core/test_poll_blocking.c   | 13 +++++++++++++
 test/core/test_select_blocking.c | 13 +++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/test/core/test_poll_blocking.c b/test/core/test_poll_blocking.c
index bdbd6b1ee1571..72981f2180a17 100644
--- a/test/core/test_poll_blocking.c
+++ b/test/core/test_poll_blocking.c
@@ -104,11 +104,19 @@ void test_unblock_poll() {
   close(pipe_shared[0]); close(pipe_shared[1]);
 }
 
+int threads_running = 0;
+pthread_mutex_t running_lock = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t running_cv = PTHREAD_COND_INITIALIZER;
+
 void *do_poll_in_thread(void * arg) {
   struct timeval begin, end;
 
   gettimeofday(&begin, NULL);
   struct pollfd fds = {pipe_shared[0], POLLIN, 0};
+  pthread_mutex_lock(&running_lock);
+  threads_running++;
+  pthread_cond_signal(&running_cv);
+  pthread_mutex_unlock(&running_lock);
   assert(poll(&fds, 1, 4000) == 1);
   gettimeofday(&end, NULL);
   assert(fds.revents & POLLIN);
@@ -130,6 +138,11 @@ void test_poll_in_threads() {
 
   assert(pthread_create(&tid1, NULL, do_poll_in_thread, NULL) == 0);
   assert(pthread_create(&tid2, NULL, do_poll_in_thread, NULL) == 0);
+  pthread_mutex_lock(&running_lock);
+  while (threads_running != 2) {
+    pthread_cond_wait(&running_cv, &running_lock);
+  }
+  pthread_mutex_unlock(&running_lock);
 
   sleep_ms(2 * TIMEOUT_MS);
   write(pipe_shared[1], t, strlen(t));
diff --git a/test/core/test_select_blocking.c b/test/core/test_select_blocking.c
index ddedab1aee851..b88dd06b821fa 100644
--- a/test/core/test_select_blocking.c
+++ b/test/core/test_select_blocking.c
@@ -108,6 +108,10 @@ void test_unblock_select() {
   close(pipe_shared[0]); close(pipe_shared[1]);
 }
 
+int threads_running = 0;
+pthread_mutex_t running_lock = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t running_cv = PTHREAD_COND_INITIALIZER;
+
 void *do_select_in_thread(void * arg) {
   struct timeval begin, end;
   fd_set readfds;
@@ -120,6 +124,10 @@ void *do_select_in_thread(void * arg) {
   int maxfd = pipe_shared[0];
 
   gettimeofday(&begin, NULL);
+  pthread_mutex_lock(&running_lock);
+  threads_running++;
+  pthread_cond_signal(&running_cv);
+  pthread_mutex_unlock(&running_lock);
   assert(select(maxfd + 1, &readfds, NULL, NULL, &tv) == 1);
   gettimeofday(&end, NULL);
   assert(FD_ISSET(pipe_shared[0], &readfds));
@@ -141,6 +149,11 @@ void test_select_in_threads() {
 
   assert(pthread_create(&tid1, NULL, do_select_in_thread, NULL) == 0);
   assert(pthread_create(&tid2, NULL, do_select_in_thread, NULL) == 0);
+  pthread_mutex_lock(&running_lock);
+  while (threads_running != 2) {
+    pthread_cond_wait(&running_cv, &running_lock);
+  }
+  pthread_mutex_unlock(&running_lock);
 
   sleep_ms(2 * TIMEOUT_MS);
   write(pipe_shared[1], t, strlen(t));