Re: [PATCH] locking: remove spin_lock_flags() etc

[Waiman Long]

On 10/25/21 11:44 AM, Arnd Bergmann wrote:
> On Mon, Oct 25, 2021 at 5:28 PM Waiman Long <longman@xxxxxxxxxx> wrote:
> > On 10/25/21 9:06 AM, Arnd Bergmann wrote:
> > > On s390, we pick between the cmpxchg() based directed-yield when
> > > running on virtualized CPUs, and a normal qspinlock when running on a
> > > dedicated CPU.
> > I am not aware that s390 is using qspinlocks at all as I don't see
> > ARCH_USE_QUEUED_SPINLOCKS being set anywhere under arch/s390. I only see
> > that it uses a cmpxchg based spinlock.
> Sorry, I should not have said "normal" here. See arch/s390/lib/spinlock.c
> for their custom queued spinlocks as implemented in arch_spin_lock_queued().
> I don't know if that code actually does the same thing as the generic qspinlock,
> but it seems at least similar.

Yes, you are right. Their queued lock code looks like a custom version 
of the pvqspinlock code.

Cheers,
Longman