Re: [PATCH] rcu: remove unnecessary check cpu_no_qs.norm on rcu_report_qs_rdp

[Yun Levi]

Hi, Paul.

Thanks for looking into this :)


> Except that rcu_report_qs_rdp() is invoked with interrupts enabled,
> which means that there is some possibility of state changes up to the
> raw_spin_lock_irqsave_rcu_node(rnp, flags) statement.
>
> So, did you check whether RCU's interrupt paths change this state?

In my narrow view,
only a new gp started, cpu_no_qs.b.norm changes as true in the path of
rcu_sched_clock_irq.
But in that case, rcu_report_qs_rdp isn't called.

Did I understand your question well and are there any missed paths I didn't see?

> Why not start with something like this?
>
>         if (!WARN_ON_ONCE(!rdp->cpu_no_qs.b.norm) ||
>             rdp->gp_seq != rnp->gp_seq || rdp->gpwrap) {
>

Yes. but with different message