netdev - Re: [PATCH v4 bpf-next 1/5] bpf: Remove redundant synchronize

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Message-ID: <CAEf4BzaLJ619mcN9pBQkupkJOcFfXWiuM8oy0Qjezy65Rpd_vA@mail.gmail.com>
Date:   Mon, 29 Jun 2020 17:58:38 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v4 bpf-next 1/5] bpf: Remove redundant synchronize_rcu.

On Mon, Jun 29, 2020 at 5:35 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> From: Alexei Starovoitov <ast@...nel.org>
>
> bpf_free_used_maps() or close(map_fd) will trigger map_free callback.
> bpf_free_used_maps() is called after bpf prog is no longer executing:
> bpf_prog_put->call_rcu->bpf_prog_free->bpf_free_used_maps.
> Hence there is no need to call synchronize_rcu() to protect map elements.
>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---

Seems correct. And nice that maps don't have to care about this anymore.

Acked-by: Andrii Nakryiko <andriin@...com>

>  kernel/bpf/arraymap.c         | 9 ---------
>  kernel/bpf/hashtab.c          | 8 +++-----
>  kernel/bpf/lpm_trie.c         | 5 -----
>  kernel/bpf/queue_stack_maps.c | 7 -------
>  kernel/bpf/reuseport_array.c  | 2 --
>  kernel/bpf/ringbuf.c          | 7 -------
>  kernel/bpf/stackmap.c         | 3 ---
>  7 files changed, 3 insertions(+), 38 deletions(-)
>