Re: [patch V6 12/37] x86/entry: Provide idtentry_entry/exit_cond_rcu()

[Thomas Gleixner]

"Paul E. McKenney" <paulmck@xxxxxxxxxx> writes:
> On Wed, May 20, 2020 at 09:51:17AM -0700, Andy Lutomirski wrote:
>> Paul, the major change here is that if an IRQ hits normal kernel code
>> (i.e. code where RCU is watching and we're not in an EQS), the IRQ
>> won't call rcu_irq_enter() and rcu_irq_exit().  Instead it will call
>> rcu_tickle() on entry and nothing on exit.  Does that cover all the
>> bases?
>
> From an RCU viewpoint, yes, give or take my concerns about someone
> putting rcu_tickle() on entry and rcu_irq_exit() on exit.  Perhaps
> I can bring some lockdep trickery to bear.

An surplus rcu_irq_exit() should already trigger alarms today.

> But I must defer to Thomas and Peter on the non-RCU/non-NO_HZ_FULL
> portions of this.

I don't see a problem. Let me write that into actual testable patch
form.

Thanks,

        tglx