linux-kernel - Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu

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Message-Id: <20200218133335.c87d7b2399ee6532bf28b74a@kernel.org>
Date:   Tue, 18 Feb 2020 13:33:35 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     paulmck@...nel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mingo@...nel.org, gregkh@...uxfoundation.org,
        gustavo@...eddedor.com, tglx@...utronix.de, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com
Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()

On Mon, 17 Feb 2020 08:31:12 -0800
"Paul E. McKenney" <paulmck@...nel.org> wrote:
> 
> > BTW, if you consider the x86 specific code is in the generic file,
> > we can move NOKPROBE_SYMBOL() in arch/x86/kernel/traps.c.
> > (Sorry, I've hit this idea right now)
> 
> Might this affect other architectures with NMIs and probe-like things?
> If so, it might make sense to leave it where it is.

Yes, git grep shows that arm64 is using rcu_nmi_enter() in
debug_exception_enter().
OK, let's keep it, but maybe it is good to update the comment for
arm64 too. What about following?

+/*
+ * All functions in do_int3() on x86, do_debug_exception() on arm64 must be
+ * marked NOKPROBE before kprobes handler is called.
+ * ist_enter() on x86 and debug_exception_enter() on arm64 which is called
+ * before kprobes handle happens to call rcu_nmi_enter() which means
+ * that rcu_nmi_enter() must be marked NOKRPOBE.
+ */

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>