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

Arnd Bergmann
2021-10-25T15:44:26Z

On Mon, Oct 25, 2021 at 5:28 PM Waiman Long <longman@redhat.com> 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.

Arnd