Re: [PATCH bpf v3] bpf: Fix RCU stall in bpf_fd_array_map_clear()

[Leon Hwang]

On 31/3/26 10:30, Sechang Lim wrote:
[...]
> Reviewed-by: Sun Jian <sun.jian.kdev@xxxxxxxxx>
> Fixes: da765a2f5993 ("bpf: Add poke dependency tracking for prog array maps")
> Signed-off-by: Sechang Lim <rhkrqnwk98@xxxxxxxxx>
> ---

After looking at v2, there's no functional change for v2 -> v3.

I think, you should send a PING in v2 after some days instead of sending
v3. If v2 will be applied, the tag will be picked up btw.

Besides, change logs are missing here.

v2 -> v3:
* ...
v2: [its lore link]

v1 -> v2:
* ...
v1: [its lore link]

Also, you should check sashiko's review [1].

[1]
https://sashiko.dev/#/patchset/20260331023056.484354-1-rhkrqnwk98%40gmail.com

>  kernel/bpf/arraymap.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 33de68c95..5e25e0353 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -1015,8 +1015,10 @@ static void bpf_fd_array_map_clear(struct bpf_map *map, bool need_defer)
>  	struct bpf_array *array = container_of(map, struct bpf_array, map);
>  	int i;
>  
> -	for (i = 0; i < array->map.max_entries; i++)
> +	for (i = 0; i < array->map.max_entries; i++) {
>  		__fd_array_map_delete_elem(map, &i, need_defer);
> +		cond_resched();

Since bpf_fd_array_map_clear() is used across prog_array,
perf_event_array, cgroup_array, and array_of_map, and this patch aims to
avoid RCU stalls for prog_array, does this cond_resched() punish
perf_event_array, cgroup_array, and array_of_map?

Thanks,
Leon

> +	}
>  }
>  
>  static void prog_array_map_seq_show_elem(struct bpf_map *map, void *key,