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SubjectRe: [PATCH] x86: eliminate TICKET_MASK
On 02/03/2012 07:06 AM, Jan Beulich wrote:
> The definition of it being questionable already (unnecessarily
> including a cast), and it being used in a single place that can be
> written shorter without it, remove this #define.
>
> Along the same lines, simplify __ticket_spin_is_locked()'s main
> expression, which was the more convoluted way because of needs that
> went away with the recent type changes by Jeremy.
>
> This is pure cleanup, no functional change intended.

That looks reasonable to me.

> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> Cc: Jeremy Fitzhardinge <jeremy@goop.org>
>
> ---
> arch/x86/include/asm/spinlock.h | 4 ++--
> arch/x86/include/asm/spinlock_types.h | 1 -
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> --- 3.3-rc2/arch/x86/include/asm/spinlock.h
> +++ 3.3-rc2-x86-ticket-mask/arch/x86/include/asm/spinlock.h
> @@ -88,14 +88,14 @@ static inline int __ticket_spin_is_locke
> {
> struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
>
> - return !!(tmp.tail ^ tmp.head);
> + return tmp.tail != tmp.head;
> }
>
> static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)
> {
> struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
>
> - return ((tmp.tail - tmp.head) & TICKET_MASK) > 1;
> + return (__ticket_t)(tmp.tail - tmp.head) > 1;
> }

Yes. I only left these unchanged the first time around because I didn't
want to inadvertently change them, but my intent was to make them more
straightforward like this.

>
> #ifndef CONFIG_PARAVIRT_SPINLOCKS
> --- 3.3-rc2/arch/x86/include/asm/spinlock_types.h
> +++ 3.3-rc2-x86-ticket-mask/arch/x86/include/asm/spinlock_types.h
> @@ -16,7 +16,6 @@ typedef u32 __ticketpair_t;
> #endif
>
> #define TICKET_SHIFT (sizeof(__ticket_t) * 8)
> -#define TICKET_MASK ((__ticket_t)((1 << TICKET_SHIFT) - 1))
>
> typedef struct arch_spinlock {
> union {
>
>
>

Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>

Thanks,
J


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