On Fri, Feb 12, 2021 at 08:20:59PM +0100, Sebastian Andrzej Siewior wrote:
> On 2020-12-09 21:27:32 [+0100], Uladzislau Rezki (Sony) wrote:
> > Add self tests for checking of RCU-tasks API functionality.
> > It covers:
> > - wait API functions;
> > - invoking/completion call_rcu_tasks*().
> >
> > Self-tests are run when CONFIG_PROVE_RCU kernel parameter is set.
>
> I just bisected to this commit. By booting with `threadirqs' I end up
> with:
> [ 0.176533] Running RCU-tasks wait API self tests
>
> No stall warning or so.
> It boots again with:
>
> diff --git a/init/main.c b/init/main.c
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1489,6 +1489,7 @@ void __init console_on_rootfs(void)
> fput(file);
> }
>
> +void rcu_tasks_initiate_self_tests(void);
> static noinline void __init kernel_init_freeable(void)
> {
> /*
> @@ -1514,6 +1515,7 @@ static noinline void __init kernel_init_freeable(void)
>
> rcu_init_tasks_generic();
> do_pre_smp_initcalls();
> + rcu_tasks_initiate_self_tests();
> lockup_detector_init();
>
> smp_init();
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -1266,7 +1266,7 @@ static void test_rcu_tasks_callback(struct rcu_head *rhp)
> rttd->notrun = true;
> }
>
> -static void rcu_tasks_initiate_self_tests(void)
> +void rcu_tasks_initiate_self_tests(void)
> {
> pr_info("Running RCU-tasks wait API self tests\n");
> #ifdef CONFIG_TASKS_RCU
> @@ -1322,7 +1322,6 @@ void __init rcu_init_tasks_generic(void)
> #endif
>
> // Run the self-tests.
> - rcu_tasks_initiate_self_tests();
> }
>
> #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
>
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
>
> Sebastian
>
We should be able to use call_rcu_tasks() in the *initcall() callbacks.
The problem is that, ksoftirqd threads are not spawned by the time when
an rcu_init_tasks_generic() is invoked:
diff --git a/init/main.c b/init/main.c
index c68d784376ca..e6106bb12b2d 100644
--- a/init/main.c
+++ b/init/main.c
@@ -954,7 +954,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
rcu_init_nohz();
init_timers();
hrtimers_init();
- softirq_init();
timekeeping_init();
/*
@@ -1512,6 +1511,7 @@ static noinline void __init kernel_init_freeable(void)
init_mm_internals();
+ softirq_init();
rcu_init_tasks_generic();
do_pre_smp_initcalls();
lockup_detector_init();
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9d71046ea247..cafa55c496d0 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -630,6 +630,7 @@ void __init softirq_init(void)
&per_cpu(tasklet_hi_vec, cpu).head;
}
+ spawn_ksoftirqd();
open_softirq(TASKLET_SOFTIRQ, tasklet_action);
open_softirq(HI_SOFTIRQ, tasklet_hi_action);
}
@@ -732,7 +733,6 @@ static __init int spawn_ksoftirqd(void)
return 0;
}
-early_initcall(spawn_ksoftirqd);
/*
* [ These __weak aliases are kept in a separate compilation unit, so that
Any thoughts?
--
Vlad Rezki
