On Tue, 18 Feb 2020 08:12:31 -0800
"Paul E. McKenney" [off-list ref] 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