linux-kernel - Re: [PATCH v2 3/8] tracing: Have syscall trace events read user space string

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Message-ID: <20250925071545.578e3643@batman.local.home>
Date: Thu, 25 Sep 2025 07:15:45 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, Masami
 Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Namhyung Kim <namhyung@...nel.org>, Takaya
 Saeki <takayas@...gle.com>, Tom Zanussi <zanussi@...nel.org>, Thomas
 Gleixner <tglx@...utronix.de>, Ian Rogers <irogers@...gle.com>, Douglas
 Raillard <douglas.raillard@....com>
Subject: Re: [PATCH v2 3/8] tracing: Have syscall trace events read user
 space string

On Thu, 25 Sep 2025 09:26:09 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> And you can't just allocate memory and not bother with the
> migrate_disable() and retry stuff because?

Because tracing is supposed to be as non-intrusive as possible. I
rather not call into the allocation system from a trace point. I'm not
sure what side effects that may cause either.

I have yet to cause the retry path under stress tests. I had to insert
a msleep() for testing purposes to make sure it worked.

-- Steve