From: Jeremy Fitzhardinge <[email protected]> Make the bulk of __ticket_spin_lock look identical for large and small number of cpus.
Signed-off-by: Jeremy Fitzhardinge <[email protected]> --- arch/x86/include/asm/spinlock.h | 23 ++++++++--------------- 1 files changed, 8 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 0170ba9..1b81809 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -70,19 +70,16 @@ static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock) #if (NR_CPUS < 256) static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) { - register union { - struct __raw_tickets tickets; - unsigned short slock; - } inc = { .slock = 1 << TICKET_SHIFT }; + register struct __raw_tickets inc = { .tail = 1 }; asm volatile (LOCK_PREFIX "xaddw %w0, %1\n" - : "+Q" (inc), "+m" (lock->slock) : : "memory", "cc"); + : "+r" (inc), "+m" (lock->tickets) : : "memory", "cc"); for (;;) { - if (inc.tickets.head == inc.tickets.tail) + if (inc.head == inc.tail) goto out; cpu_relax(); - inc.tickets.head = ACCESS_ONCE(lock->tickets.head); + inc.head = ACCESS_ONCE(lock->tickets.head); } out: barrier(); /* make sure nothing creeps before the lock is taken */ } @@ -108,21 +105,17 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock) #else static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) { - unsigned inc = 1 << TICKET_SHIFT; - __ticket_t tmp; + register struct __raw_tickets inc = { .tail = 1 }; asm volatile(LOCK_PREFIX "xaddl %0, %1\n\t" - : "+r" (inc), "+m" (lock->slock) + : "+r" (inc), "+m" (lock->tickets) : : "memory", "cc"); - tmp = inc; - inc >>= TICKET_SHIFT; - for (;;) { - if ((__ticket_t)inc == tmp) + if (inc.head == inc.tail) goto out; cpu_relax(); - tmp = ACCESS_ONCE(lock->tickets.head); + inc.head = ACCESS_ONCE(lock->tickets.head); } out: barrier(); /* make sure nothing creeps before the lock is taken */ } -- 1.7.2.3 _______________________________________________ Virtualization mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/virtualization
