linux-kernel - Re: [PATCH perf/core 07/22] uprobes: Remove breakpoint in unapply_uprobe under mmap_write

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Message-ID: <20250428114051.GD27775@redhat.com>
Date: Mon, 28 Apr 2025 13:40:52 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...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>,
	Masami Hiramatsu <mhiramat@...nel.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: [PATCH perf/core 07/22] uprobes: Remove breakpoint in
 unapply_uprobe under mmap_write_lock

On 04/28, Jiri Olsa wrote:
>
> On Sun, Apr 27, 2025 at 04:24:01PM +0200, Oleg Nesterov wrote:
> >
> > And perhaps the comment above mmap_write_lock() in register_for_each_vma()
> > should be updated too... or even removed.
>
> hum, not sure now how it's related to this change, but will stare at it bit more

That comment tries to explain why register_for_each_vma() has to take
mm->mmap_lock for writing. Without the described race it could use
mmap_read_lock(). See 84455e6923c79 for the details.

Now that we have another (obvious) reason for mmap_write_lock(mm), this
comment looks confusing.

Oleg.