On Tue, Jun 14, 2022 at 08:06:20AM -0400, Waiman Long wrote:
> 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 perhaps
> delaying other late_initcall's queued after it by a second or more.
> Fix this by using delayed_work to repeat the verification check instead.
>
> Fixes: 2585014188d5 ("rcu-tasks: Be more patient for RCU Tasks boot-time testing")
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Applied, thank you!
Thanx, Paul
> ---
> kernel/rcu/tasks.h | 35 ++++++++++++++++++++++++++++++++---
> 1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index fcbd0ec33c86..e151cd5ae2bc 100644
> --- 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 +1852,40 @@ static int rcu_tasks_verify_self_tests(void)
> ret = -1;
> break;
> }
> - schedule_timeout_uninterruptible(1);
> + ret = 1;
> + break;
> }
> }
>
> - if (ret)
> + if (ret < 0)
> WARN_ON(1);
>
> 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 */
> --
> 2.31.1
>
