[glib: 1/3] test: Potentially fix a race in thread-pool-slow test

[Marco Trevisan <marcotrevi src gnome org>]

commit afc08836522c84c6d04a81b971d58434711f0666
Author: Philip Withnall <pwithnall endlessos org>
Date:   Wed May 18 15:37:19 2022 +0100

    test: Potentially fix a race in thread-pool-slow test
    
    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 7f497418cb..cef02db778 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 ();