linux-kernel - Re: [PATCHv6 perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines

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Message-ID: <aKW9Mrbj_6H9MXrm@krava>
Date: Wed, 20 Aug 2025 14:18:58 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Andrii Nakryiko <andrii@...nel.org>,
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, x86@...nel.org,
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...lab.com>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv6 perf/core 08/22] uprobes/x86: Add mapping for optimized
 uprobe trampolines

On Tue, Aug 19, 2025 at 04:53:45PM +0200, Peter Zijlstra wrote:
> On Sun, Jul 20, 2025 at 01:21:18PM +0200, Jiri Olsa wrote:
> > +static void destroy_uprobe_trampoline(struct uprobe_trampoline *tramp)
> > +{
> > +	/*
> > +	 * We do not unmap and release uprobe trampoline page itself,
> > +	 * because there's no easy way to make sure none of the threads
> > +	 * is still inside the trampoline.
> > +	 */
> > +	hlist_del(&tramp->node);
> > +	kfree(tramp);
> > +}
> 
> I am somewhat confused; isn't this called from
> __mmput()->uprobe_clear_state()->arch_uprobe_clear_state ?
> 
> At that time we don't have threads anymore and mm is about to be
> destroyed anyway.

ah you mean the comment, right? we need to release tramp objects

the comment is leftover from some of the previous version, it can be
removed, sorry

jirka