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
