linux-kernel - Re: [PATCH] btf: Simplify BTF logic with use of __free(btf

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Message-ID: <CAADnVQJnTqXLNT9YWWkpLqjxw7MGMrq_CTT7Dhb__R0uO2-COA@mail.gmail.com>
Date: Fri, 1 Aug 2025 08:28:50 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, 
	Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	KP Singh <kpsingh@...nel.org>
Subject: Re: [PATCH] btf: Simplify BTF logic with use of __free(btf_put)

On Fri, Aug 1, 2025 at 8:19 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 1 Aug 2025 08:12:08 -0700
> Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
>
> >
> > You can use it in kernel/trace/trace_output.c, of course,
>
> I guess that means I should just use the DEFINE_FREE() in that file
> directly and not in the btf.h header file?

yes. I don't want this to proliferate and people spam us
with this kind of "cleanups".

> > but I really think it's a step back in maintainability.
> > All this cleanup.h is not a silver bullet. It needs to be used sparingly.
>
> I have my reservations about the cleanup.h code too. But the more I use it,
> the more I like it. My biggest worry is guard() leak. That is, having a
> lock or interrupt/preemption disabled for longer than they need to be,
> because code was added at the end of the function after the protection is
> needed.

guard() is ok. We use it too,
but __free() is imo garbage. It's essence of what's wrong with C++