Re: [PATCH RFC bpf-next 1/2] bpf: Keep recursion-checked trampoline programs non-preemptible on !PREEMPT_RT

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] bpf: multi-line comment style violation in __bpf_prog_enter_recur()
--

commit 264a83620cb7c053d29054a8d674730e0e75ac83
Author: Mike Bazov <mikeba@sentinelone.com>

bpf: Keep recursion-checked trampoline programs non-preemptible on !PREEMPT_RT

This commit disables preemption in __bpf_prog_enter_recur() and
__bpf_prog_exit_recur() when CONFIG_PREEMPT_RT is disabled so that
per-CPU recursion tracking and per-CPU private stacks are not shared
across preempted tasks on the same CPU.

> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index bf4cb3dd444d6..632c104112b2e 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -1339,7 +1339,15 @@ static __always_inline u64 notrace bpf_prog_start_time(void)
>  static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
>  	__acquires(RCU)
>  {
> -	rcu_read_lock_dont_migrate();
> +	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> +		rcu_read_lock_dont_migrate();
> +	} else {
> +		/* prog->active and the private stack are per-CPU: don't let
> +		 * another task run on this CPU while we hold them.
> +		 */

[Severity: Low]
This isn't a bug, but in __bpf_prog_enter_recur() in
kernel/bpf/trampoline.c, could this multi-line comment place the opening
/* on its own line to follow the BPF subsystem comment style?

		/*
		 * prog->active and the private stack are per-CPU: don't let
		 * another task run on this CPU while we hold them.
		 */

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261025-b4-bpf-trampoline-preempt-v1-0-198dcdc0c6ac@sentinelone.com?part=1