rcu-tasks: Use delayed_work to delay rcu_tasks_verify_self_tests()

Commit 2585014188d5 ("rcu-tasks: Be more patient for RCU Tasks
boot-time testing") fixes false positive rcu_tasks verification check
failure by repeating the test once every second until timeout using
schedule_timeout_uninterruptible().

Since rcu_tasks_verify_selft_tests() is called from do_initcalls()
as a late_initcall, this has the undesirable side effect of delaying
other late_initcall's queued after it by a second or more.  Fix this by
instead using delayed_work to repeat the verification check.

Fixes: 2585014188d5 ("rcu-tasks: Be more patient for RCU Tasks boot-time testing")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index fcbd0ec..83c7e66 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1832,6 +1832,11 @@ static void rcu_tasks_initiate_self_tests(void)
 #endif
 }
 
+/*
+ * Return:  0 - test passed
+ *         1 - test failed, but have not timed out yet
+ *        -1 - test failed and timed out
+ */
 static int rcu_tasks_verify_self_tests(void)
 {
        int ret = 0;
@@ -1847,16 +1852,38 @@ static int rcu_tasks_verify_self_tests(void)
                                ret = -1;
                                break;
                        }
-                       schedule_timeout_uninterruptible(1);
+                       ret = 1;
+                       break;
                }
        }
-
-       if (ret)
-               WARN_ON(1);
+       WARN_ON(ret < 0);
 
        return ret;
 }
-late_initcall(rcu_tasks_verify_self_tests);
+
+/*
+ * Repeat the rcu_tasks_verify_self_tests() call once every second until the
+ * test passes or has timed out.
+ */
+static struct delayed_work rcu_tasks_verify_work;
+static void rcu_tasks_verify_work_fn(struct work_struct *work __maybe_unused)
+{
+       int ret = rcu_tasks_verify_self_tests();
+
+       if (ret <= 0)
+               return;
+
+       /* Test fails but not timed out yet, reschedule another check */
+       schedule_delayed_work(&rcu_tasks_verify_work, HZ);
+}
+
+static int rcu_tasks_verify_schedule_work(void)
+{
+       INIT_DELAYED_WORK(&rcu_tasks_verify_work, rcu_tasks_verify_work_fn);
+       rcu_tasks_verify_work_fn(NULL);
+       return 0;
+}
+late_initcall(rcu_tasks_verify_schedule_work);
 #else /* #ifdef CONFIG_PROVE_RCU */
 static void rcu_tasks_initiate_self_tests(void) { }
 #endif /* #else #ifdef CONFIG_PROVE_RCU */