linux-kernel - Re: [GIT PULL] probes: Update for v6.18

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Message-ID: <CAHk-=wg6=DwTD7xT3=Zya-ytYrtS2969KtnTWRPskq5fx2Ev+g@mail.gmail.com>
Date: Sun, 5 Oct 2025 09:20:29 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Menglong Dong <menglong8.dong@...il.com>, Thorsten Blum <thorsten.blum@...ux.dev>, 
	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] probes: Update for v6.18

On Thu, 2 Oct 2025 at 16:44, Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> - wprobe: Introduce a watchpoint probe event based on hw_breakpoint.

This doesn't even build.

  kernel/trace/trace_wprobe.c: In function ‘__register_trace_wprobe’:
  kernel/trace/trace_wprobe.c:176:20: error: cast to generic address
space pointer from disjoint ‘__seg_gs’ address space pointer [-Werror]

and I see from the code that it has tried to brute-force it with an
ugly cast, and it still is horribly horribly wrong.

The fix for compiler errors is basically never to just add a random
cast. That will just make things worse, and in this case that
'IS_ERR()' function literally exists to find bad users like this.

I wondered why this hadn't been reported in linux-next, and the reason
appears simple: none of this has BEEN in linux-next.

So no. I'm not pulling this. This violates all the regular rules for
sending me new development, and then it doesn't even compile.

Since the pointer is a percpu pointer, the trivial fix is ato use the
per-cpu specific functions (IS_ERR_PCPU(), PTR_ERR_PCPU(), etc).

However, since this wasn't in linux-next, that's not what I'm doing.

This is not getting pulled for 6.18 AT ALL, and for 6.19 it had better
be in linux-next for a LOONG time.

           Linus