Re: [PATCH 1/2] sched/idle: Fix arch_cpu_idle() vs tracing

[Peter Zijlstra]

On Mon, Nov 30, 2020 at 01:00:03PM -0800, Guenter Roeck wrote:
> On Fri, Nov 20, 2020 at 12:41:46PM +0100, Peter Zijlstra wrote:
> > We call arch_cpu_idle() with RCU disabled, but then use
> > local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.
> > 
> > Switch all arch_cpu_idle() implementations to use
> > raw_local_irq_{en,dis}able() and carefully manage the
> > lockdep,rcu,tracing state like we do in entry.
> > 
> > (XXX: we really should change arch_cpu_idle() to not return with
> > interrupts enabled)
> > 
> 
> Has this patch been tested on s390 ? Reason for asking is that it causes
> all my s390 emulations to crash. Reverting it fixes the problem.

My understanding is that it changes the error on s390. Previously it
would complain about the local_irq_enable() in arch_cpu_idle(), now it
complains when taking an interrupt during idle.