On Fri, Feb 19, 2021 at 09:17:55AM +0100, Sebastian Andrzej Siewior wrote:
> On 2021-02-18 07:15:54 [-0800], Paul E. McKenney wrote:
> > Thank you, but the original report of a problem was from Sebastian
> > and the connection to softirq was Uladzislau. So could you please
> > add these before (or even in place of) my Reported-by?
> >
> > Reported-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> > Reported-by: Uladzislau Rezki <urezki@xxxxxxxxx>
> >
> > Other than that, looks good!
>
> Perfect. I'm kind of lost here, nevertheless ;) Does this mean that the
> RCU selftest can now be delayed?
>
If above fix works, we can initialize rcu_init_tasks_generic() from the
core_initcall() including selftst. It means that such initialization can
be done later:
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 5cc6deaa5df2..ae7d0cdfa9bd 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -88,12 +88,6 @@ void rcu_sched_clock_irq(int user);
void rcu_report_dead(unsigned int cpu);
void rcutree_migrate_callbacks(int cpu);
-#ifdef CONFIG_TASKS_RCU_GENERIC
-void rcu_init_tasks_generic(void);
-#else
-static inline void rcu_init_tasks_generic(void) { }
-#endif
-
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);
void rcu_sysrq_end(void);
diff --git a/init/main.c b/init/main.c
index c68d784376ca..3024c4db17a9 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1512,7 +1512,6 @@ static noinline void __init kernel_init_freeable(void)
init_mm_internals();
- rcu_init_tasks_generic();
do_pre_smp_initcalls();
lockup_detector_init();
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 17c8ebe131af..2797f9a042f4 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -966,11 +966,6 @@ static void rcu_tasks_trace_pregp_step(void)
static void rcu_tasks_trace_pertask(struct task_struct *t,
struct list_head *hop)
{
- // During early boot when there is only the one boot CPU, there
- // is no idle task for the other CPUs. Just return.
- if (unlikely(t == NULL))
- return;
-
WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
WRITE_ONCE(t->trc_reader_checked, false);
t->trc_ipi_to_cpu = -1;
@@ -1300,7 +1295,7 @@ late_initcall(rcu_tasks_verify_self_tests);
static void rcu_tasks_initiate_self_tests(void) { }
#endif /* #else #ifdef CONFIG_PROVE_RCU */
-void __init rcu_init_tasks_generic(void)
+static void __init rcu_init_tasks_generic(void)
{
#ifdef CONFIG_TASKS_RCU
rcu_spawn_tasks_kthread();
@@ -1318,6 +1313,7 @@ void __init rcu_init_tasks_generic(void)
rcu_tasks_initiate_self_tests();
}
+core_initcall(rcu_init_tasks_generic);
#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
static inline void rcu_tasks_bootup_oddness(void) {}
void show_rcu_tasks_gp_kthreads(void) {}
--
Vlad Rezki
