linux-kernel - Re: [PATCH] bpf: defer printk() inside __bpf_prog

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Message-ID: <3b332a67-b1ef-4448-9a75-66d9638edeaa@I-love.SAKURA.ne.jp>
Date: Thu, 27 Jun 2024 09:00:26 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        Alexei Starovoitov
 <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau
 <martin.lau@...ux.dev>,
        Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: defer printk() inside __bpf_prog_run()

On 2024/06/27 8:52, Alexei Starovoitov wrote:
>>> Sorry, but it makes no sense to put the burden of the
>>> printk_deferred_enter() on the BPF hook logic. It should sit solely
>>> with the code that actually calls printk().
>>
>> How do you respond to Petr Mladek's comment
>>
>>   Yeah, converting printk() into printk_deferred() or using
>>   printk_deferred_enter() around particular code paths is a whac-a-mole
>>   game.
> 
> Exactly. wrapping bpf with printk_deferred_enter() is such a whac-a-mole.
> It doesn't fix an issue.

Then, what change do you propose?