Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()

Masami Hiramatsu
2020-02-18T04:33:41Z

On Mon, 17 Feb 2020 08:31:12 -0800
"Paul E. McKenney" <paulmck@kernel.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@kernel.org>