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From: Steven Rostedt <rostedt@goodmis.org>
To: Roland Ruckerbauer <roland.rucky@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	linux-kernel@vger.kernel.org, Takashi Iwai <tiwai@suse.de>,
	regressions@lists.linux.dev,
	Steven Noonan <steven.noonan@gmail.com>
Subject: Re: [BUG] NULL pointer dereference probably caused by kernel/trace/ring_buffer.c
Date: Tue, 1 Nov 2022 18:35:12 -0400	[thread overview]
Message-ID: <20221101183512.285cfd68@rorschach.local.home> (raw)
In-Reply-To: <CAM6WdxfsP13aS62=xWNTFEEzAekAuDwFTpnONP9qF3br-65KWQ@mail.gmail.com>

On Tue, 1 Nov 2022 23:01:38 +0100
Roland Ruckerbauer <roland.rucky@gmail.com> wrote:

> Just figured out something, the poll() errors starting at fd 29 (which
> is CPU 24).
> But I only have 24 cores. Looked at
> /sys/kernel/debug/tracing/instances/rasdaemon/per_cpu/, and voila, it
> lists 32 cpus not 24.

Ah, and this explains why I never triggered it. There's some machines
that list nr_cpu_ids as more than what exists (I guess it is "possible
CPUs" and not "actual CPUs").

OK, this is a great clue. I'll dig deeper.

Thanks a lot for telling me this.

Takashi, can you check if the problem machines have more CPUs listed in
/sys/kernel/tracing/per_cpu/cpu* than is on the machine?

-- Steve

  reply	other threads:[~2022-11-01 22:36 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-31 13:02 Roland Ruckerbauer
2022-10-31 13:24 ` Steven Rostedt
2022-10-31 18:50 ` Steven Rostedt
2022-10-31 20:20   ` Roland Ruckerbauer
2022-11-01 19:31     ` Steven Rostedt
2022-11-01 20:07       ` Roland Ruckerbauer
2022-11-01 21:38         ` Steven Rostedt
2022-11-01 21:50           ` Roland Ruckerbauer
2022-11-01 22:01             ` Roland Ruckerbauer
2022-11-01 22:35               ` Steven Rostedt [this message]
2022-11-01 22:43                 ` Steven Rostedt
2022-11-01 23:00                   ` Roland Ruckerbauer

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