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

[Steven Rostedt]

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