On 27.03.2024 16:22, Juergen Gross wrote: > Allow 16 bits per cpu number, which is the limit imposed by > spinlock_tickets_t. > > This will allow up to 65535 cpus, while increasing only the size of > recursive spinlocks in debug builds from 8 to 12 bytes. > > The current Xen limit of 4095 cpus is imposed by SPINLOCK_CPU_BITS > being 12. There are machines available with more cpus than the current > Xen limit, so it makes sense to have the possibility to use more cpus. > > Signed-off-by: Juergen Gross <jgr...@suse.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com> albeit I have to say that I'm not entirely convinced of ... > --- a/xen/common/spinlock.c > +++ b/xen/common/spinlock.c > @@ -485,7 +485,9 @@ bool _rspin_trylock(rspinlock_t *lock) > > /* Don't allow overflow of recurse_cpu field. */ > BUILD_BUG_ON(NR_CPUS > SPINLOCK_NO_CPU); > + BUILD_BUG_ON(SPINLOCK_CPU_BITS > sizeof(lock->recurse_cpu) * 8); > BUILD_BUG_ON(SPINLOCK_RECURSE_BITS < 3); > + BUILD_BUG_ON(SPINLOCK_MAX_RECURSE > ((1u << SPINLOCK_RECURSE_BITS) - 1)); > > check_lock(&lock->debug, true); ... the two additions here: The two checks we had verify independent properties, whereas the new ones basically check that struct rspinlock and its associated #define-s were got right. We don't check such elsewhere, I don't think. Jan
