Re: [RFC PATCH 1/2] rcu: Add rcu_read_lock_notrace()

["Paul E. McKenney" <paulmck@kernel.org>]

On Thu, Jul 17, 2025 at 11:55:10AM -0400, Steven Rostedt wrote:
> On Thu, 17 Jul 2025 11:40:28 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > Yes, it is a tracepoint infra problem that we are trying to solve. The
> > reason we are trying to solve it is because BPF programs can extend the
> > time a tracepoint takes. If anything else extended the time, this would
> > need to be solved as well. But currently it's only BPF programs that
> > cause the issue.
> 
> BTW, if we can't solve this issue and something else came along and
> attached to tracepoints that caused unbounded latency, I would also
> argue that whatever came along would need to be prevented from being
> configured with PREEMPT_RT. My comment wasn't a strike against BPF
> programs; It was a strike against something adding unbounded latency
> into a critical section that has preemption disabled.

I would imagine that many PREEMPT_RT installations would have a severe
and heavy-weight review, test, and approval process for BPF programs
intended for use in production systems...

							Thanx, Paul