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

Steven Rostedt
2020-02-18T16:35:06Z

On Tue, 18 Feb 2020 08:12:31 -0800
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> Would it work to describe the general problem, then give x86 details
> as a specific example, as follows?
>
> /*
> * On some architectures, certain exceptions prohibit use of kprobes until
> * the exception code path reaches a certain point. For example, on x86 all
> * functions called by do_int3() must be marked NOKPROBE. However, once
> * kprobe_int3_handler() is called, kprobing is permitted. Specifically,
> * ist_enter() is called in do_int3() before kprobe_int3_handle().
> * Furthermore, ist_enter() calls rcu_nmi_enter(), which means that
> * rcu_nmi_enter() must be marked NOKRPOBE.
> */
>
> That way, I don't feel like I need to update the commment each time
> a new architecture adds this capability. ;-)

I don't think this is going to be an issue for other archs, as they
don't have an IST.

-- Steve