From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Josef Bacik <josef@toxicpanda.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
rcu@vger.kernel.org
Subject: Re: [PATCH] fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()
Date: Thu, 1 Oct 2026 13:23:49 +0000 [thread overview]
Message-ID: <20261001132349.472186a7@mhiramat99.roam.internal> (raw)
In-Reply-To: <20260930160325.3f2621ea@fedora>
On Wed, 30 Sep 2026 16:03:25 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 29 Sep 2026 09:19:12 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > @@ -329,16 +333,14 @@ static void fprobe_ftrace_entry(unsigned long
> > ip, unsigned long parent_ip, struct fprobe *fp;
> > int bit;
> >
> > + if (!rcu_is_watching())
> > + return;
> > +
>
> I'm thinking these should really be:
>
> if (WARN_ON_ONCE(!rcu_is_watching()))
> return;
Hmm, is this for warning users to notice it is out of supported path?
If CONFIG_ARCH_WANTS_NO_INSTR=n, we will not prohibit user to set ftrace
avoiding the function where the RCU is not watching. So maybe it is hit
by user's operation.
Thank you,
>
> -- Steve
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
prev parent reply other threads:[~2026-10-01 13:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-29 0:19 [PATCH] fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() Masami Hiramatsu (Google)
2026-09-30 18:47 ` Paul E. McKenney
2026-09-30 20:03 ` Steven Rostedt
2026-10-01 13:23 ` Masami Hiramatsu (Google) [this message]
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