From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by smtp.lore.kernel.org (Postfix) with ESMTP id D5408C7EE23
	for <linux-kernel@archiver.kernel.org>; Tue, 23 May 2023 14:11:51 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S236612AbjEWOLt (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Tue, 23 May 2023 10:11:49 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47498 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S236869AbjEWOL1 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 23 May 2023 10:11:27 -0400
Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7973FC4;
        Tue, 23 May 2023 07:10:46 -0700 (PDT)
Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140])
        (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
        (No client certificate requested)
        by dfw.source.kernel.org (Postfix) with ESMTPS id 2876160B02;
        Tue, 23 May 2023 14:10:45 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 095CFC433D2;
        Tue, 23 May 2023 14:10:42 +0000 (UTC)
Date:   Tue, 23 May 2023 10:10:41 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Ze Gao <zegao2021@gmail.com>
Cc:     Jiri Olsa <olsajiri@gmail.com>, Yonghong Song <yhs@meta.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Hao Luo <haoluo@google.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Song Liu <song@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Yonghong Song <yhs@fb.com>, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        kafai@fb.com, kpsingh@chromium.org, netdev@vger.kernel.org,
        paulmck@kernel.org, songliubraving@fb.com,
        Ze Gao <zegao@tencent.com>
Subject: Re: kprobes and rcu_is_watching()
Message-ID: <20230523101041.23ca7cc8@rorschach.local.home>
In-Reply-To: <CAD8CoPDASe7hpkFbK+UzJats7j4sbgsCh_P4zaQYVuKD7jWu2w@mail.gmail.com>
References: <20220515203653.4039075-1-jolsa@kernel.org>
        <20230520094722.5393-1-zegao@tencent.com>
        <b4f66729-90ab-080a-51ec-bf435ad6199d@meta.com>
        <CAD8CoPAXse1GKAb15O5tZJwBqMt1N_btH+qRe7c_a-ryUMjx7A@mail.gmail.com>
        <ZGp+fW855gmWuh9W@krava>
        <CAD8CoPDASe7hpkFbK+UzJats7j4sbgsCh_P4zaQYVuKD7jWu2w@mail.gmail.com>
X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

[ Added a subject, as I always want to delete these emails as spam! ]

On Mon, 22 May 2023 10:07:42 +0800
Ze Gao <zegao2021@gmail.com> wrote:

> Oops, I missed that. Thanks for pointing that out, which I thought is
> conditional use of rcu_is_watching before.
> 
> One last point, I think we should double check on this
>      "fentry does not filter with !rcu_is_watching"
> as quoted from Yonghong and argue whether it needs
> the same check for fentry as well.
> 

Note that trace_test_and_set_recursion() (which is used by
ftrace_test_recursion_trylock()) checks for rcu_is_watching() and
returns false if it isn't (and the trylock will fail).

-- Steve