From afc08836522c84c6d04a81b971d58434711f0666 Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@endlessos.org>
Date: Wed, 18 May 2022 15:37:19 +0100
Subject: [PATCH] test: Potentially fix a race in thread-pool-slow test
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It’s failed on a CI machine
(https://gitlab.gnome.org/GNOME/glib/-/jobs/2006694) with log:
```
[unused] => pushed 100 threads onto the idle pool
[unused] stopping unused threads
[unused] waiting ONE second for threads to die
[unused] waiting ONE second for threads to die
[unused] waiting ONE second for threads to die
[unused] waiting ONE second for threads to die
[unused] waiting ONE second for threads to die
[unused] stopped idle threads, 9 remain
Bail out! GLib:ERROR:../glib/tests/thread-pool-slow.c:113:test_thread_stop_unused: assertion failed (g_thread_pool_get_num_unused_threads () == 0): (9 == 0)
```

I can’t reproduce this locally, but it’s possible that it failed because
a one second wait was not enough to enqueue all the jobs (on a heavily
loaded machine), and hence some jobs spawned thread pool threads after
calling `g_thread_pool_stop_unused_threads()`, leading to the assertion
failure.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
---
 glib/tests/thread-pool-slow.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/glib/tests/thread-pool-slow.c b/glib/tests/thread-pool-slow.c
index 7f497418c..cef02db77 100644
--- a/glib/tests/thread-pool-slow.c
+++ b/glib/tests/thread-pool-slow.c
@@ -61,22 +61,36 @@ test_thread_functions (void)
   g_assert_cmpint (g_thread_pool_get_max_idle_time (), ==, 0);
 }
 
+static void
+thread_wait_func (gpointer data,
+                  gpointer user_data)
+{
+  guint timeout_ms = GPOINTER_TO_UINT (data);
+  guint *n_threads_executed = user_data;
+
+  g_usleep (timeout_ms);
+
+  g_atomic_int_inc (n_threads_executed);
+}
+
 static void
 test_thread_stop_unused (void)
 {
    GThreadPool *pool;
    guint i;
    guint limit = 100;
+   guint n_threads_executed = 0;
 
    /* Spawn a few threads. */
    g_thread_pool_set_max_unused_threads (-1);
-   pool = g_thread_pool_new ((GFunc) g_usleep, NULL, -1, FALSE, NULL);
+   pool = g_thread_pool_new (thread_wait_func, &n_threads_executed, -1, FALSE, NULL);
 
    for (i = 0; i < limit; i++)
      g_thread_pool_push (pool, GUINT_TO_POINTER (1000), NULL);
 
    /* Wait for the threads to migrate. */
-   g_usleep (G_USEC_PER_SEC);
+   while ((guint) g_atomic_int_get (&n_threads_executed) < limit)
+     g_usleep (100);
 
    g_thread_pool_stop_unused_threads ();