netdev - Re: [PATCH bpf-next] bpf: Allow bpf_current_task_under

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Date:   Sat, 28 Apr 2018 08:03:19 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Teng Qin <qinteng@...com>, <netdev@...r.kernel.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <yhs@...com>,
        <kernel-team@...com>
Subject: Re: [PATCH bpf-next] bpf: Allow bpf_current_task_under_cgroup in
 interrupt

On 4/28/18 12:32 AM, Teng Qin wrote:
> Currently, the bpf_current_task_under_cgroup helper has a check where if
> the BPF program is running in_interrupt(), it will return -EINVAL. This
> prevents the helper to be used in many useful scenarios, particularly
> BPF programs attached to Perf Events.
>
> This commit removes the check. Tested a few NMI (Perf Event) and some
> softirq context, the helper returns the correct result.
> ---
>  kernel/trace/bpf_trace.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 56ba0f2..f94890c 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -474,8 +474,6 @@ BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
>  	struct bpf_array *array = container_of(map, struct bpf_array, map);
>  	struct cgroup *cgrp;
>
> -	if (unlikely(in_interrupt()))
> -		return -EINVAL;
>  	if (unlikely(idx >= array->map.max_entries))
>  		return -E2BIG;
>

looks good, but SOB is missing. Please respin.