2021-12-26 00:52:24

by Zqiang

Subject: [PATCH v2] rcu, kasan: Record work creation stack trace with interrupts enabled

Recording the work creation stack trace for KASAN reports in
call_rcu() is expensive, due to unwinding the stack, but also
due to acquiring depot_lock inside stackdepot (which may be contended).
Because calling kasan_record_aux_stack_noalloc() does not require
interrupts to already be disabled, this may unnecessarily extend
the time with interrupts disabled.

Therefore, move calling kasan_record_aux_stack() before the section
with interrupts disabled.

Acked-by: Marco Elver <[email protected]>
Signed-off-by: Zqiang <[email protected]>
---
v1->v2:
Make the submitted information clearer.

kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9b58bae0527a..36bd3f9e57b3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3068,8 +3068,8 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
}
head->func = func;
head->next = NULL;
- local_irq_save(flags);
kasan_record_aux_stack_noalloc(head);
+ local_irq_save(flags);
rdp = this_cpu_ptr(&rcu_data);

/* Add the callback to our list. */
--
2.25.1

2021-12-28 16:17:53

by Paul E. McKenney

Subject: Re: [PATCH v2] rcu, kasan: Record work creation stack trace with interrupts enabled

On Sun, Dec 26, 2021 at 08:52:04AM +0800, Zqiang wrote:
> Recording the work creation stack trace for KASAN reports in
> call_rcu() is expensive, due to unwinding the stack, but also
> due to acquiring depot_lock inside stackdepot (which may be contended).
> Because calling kasan_record_aux_stack_noalloc() does not require
> interrupts to already be disabled, this may unnecessarily extend
> the time with interrupts disabled.
>
> Therefore, move calling kasan_record_aux_stack() before the section
> with interrupts disabled.
>
> Acked-by: Marco Elver <[email protected]>
> Signed-off-by: Zqiang <[email protected]>

Applied, thank you both!

Thanx, Paul

> ---
> v1->v2:
> Make the submitted information clearer.
>
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9b58bae0527a..36bd3f9e57b3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3068,8 +3068,8 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
> }
> head->func = func;
> head->next = NULL;
> - local_irq_save(flags);
> kasan_record_aux_stack_noalloc(head);
> + local_irq_save(flags);
> rdp = this_cpu_ptr(&rcu_data);
>
> /* Add the callback to our list. */
> --
> 2.25.1
>