On Wed, Dec 09, 2020 at 09:27:31PM +0100, Uladzislau Rezki (Sony) wrote:
> Initialize the RCU-tasks earlier, before *_initcall() callbacks are
> invoked. Do it after the workqueue subsytem is up and running. That
> gives us a possibility to make use of synchronize_rcu_tasks*() wait
> API in early_initcall() callbacks.
>
> Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall")
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Thank you! I have queued both with the usual editing, so please
check and let me know if I messed something up.
Thanx, Paul
> ---
> include/linux/rcupdate.h | 6 ++++++
> init/main.c | 1 +
> kernel/rcu/tasks.h | 26 ++++++++++++++++++++++----
> 3 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 3c3efa4d6ab5..340c7d5344a4 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -88,6 +88,12 @@ 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 130376ec10ba..e253e87bdf58 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1502,6 +1502,7 @@ 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 35bdcfd84d42..67a162949763 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -241,7 +241,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
> }
> }
>
> -/* Spawn RCU-tasks grace-period kthread, e.g., at core_initcall() time. */
> +/* Spawn RCU-tasks grace-period kthread. */
> static void __init rcu_spawn_tasks_kthread_generic(struct rcu_tasks *rtp)
> {
> struct task_struct *t;
> @@ -564,7 +564,6 @@ static int __init rcu_spawn_tasks_kthread(void)
> rcu_spawn_tasks_kthread_generic(&rcu_tasks);
> return 0;
> }
> -core_initcall(rcu_spawn_tasks_kthread);
>
> #if !defined(CONFIG_TINY_RCU)
> void show_rcu_tasks_classic_gp_kthread(void)
> @@ -692,7 +691,6 @@ static int __init rcu_spawn_tasks_rude_kthread(void)
> rcu_spawn_tasks_kthread_generic(&rcu_tasks_rude);
> return 0;
> }
> -core_initcall(rcu_spawn_tasks_rude_kthread);
>
> #if !defined(CONFIG_TINY_RCU)
> void show_rcu_tasks_rude_gp_kthread(void)
> @@ -968,6 +966,12 @@ 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 one boot-CPU,
> + // an idle_task is not set for other CPUs. In this case
> + // just revert.
> + 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;
> @@ -1193,7 +1197,6 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
> rcu_spawn_tasks_kthread_generic(&rcu_tasks_trace);
> return 0;
> }
> -core_initcall(rcu_spawn_tasks_trace_kthread);
>
> #if !defined(CONFIG_TINY_RCU)
> void show_rcu_tasks_trace_gp_kthread(void)
> @@ -1222,6 +1225,21 @@ void show_rcu_tasks_gp_kthreads(void)
> }
> #endif /* #ifndef CONFIG_TINY_RCU */
>
> +void __init rcu_init_tasks_generic(void)
> +{
> +#ifdef CONFIG_TASKS_RCU
> + rcu_spawn_tasks_kthread();
> +#endif
> +
> +#ifdef CONFIG_TASKS_RUDE_RCU
> + rcu_spawn_tasks_rude_kthread();
> +#endif
> +
> +#ifdef CONFIG_TASKS_TRACE_RCU
> + rcu_spawn_tasks_trace_kthread();
> +#endif
> +}
> +
> #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
> static inline void rcu_tasks_bootup_oddness(void) {}
> void show_rcu_tasks_gp_kthreads(void) {}
> --
> 2.20.1
>
