On Thu, 16 Apr 2020 18:33:02 +0200
Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> > > > You mean that in CONFIG_PREEMPT_RT:
> > > >
> > > > <snip>
> > > > local_irq_save(flags);
> > > > krcp = this_cpu_ptr(&krc);
> > > > spin_lock(&krcp->lock);
> > > > <snip>
> > > >
> > > > it will not be preempted, what does not follow PREEMPT_RT policy. Is that correct?
> > >
> > > No. local_irq_save() disables interrupts and spin_lock() acquires a
> > > sleeping lock which may schedule() if contended. The documentation has
> > > this piece:
> > >
> > Ah. Got it. Then it is a problem, agree. Do you have something
> > that would guarantee of being staying on the same CPU?
> > migration_disable()?
>
> migrate_disable() would work.
I wonder if we should have a this_cpu_spin_lock_irqsave(), that would
encapsulate the migrate_disable()?
static inline this_cpu_spin_lock_irqsave(struct spinlock __per_cpu *lock)
{
migrate_disable();
spin_lock_irqsave(this_cpu_ptr(lock));
migrate_enable();
}
?
-- Steve
