From dc126c03ca25de516eaa8e575a98b81382d6d4b4 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Thu, 23 Jun 2011 18:19:16 -0700 Subject: [PATCH] x86, ticketlock: Make large and small ticket versions of spin_lock the same Make the bulk of __ticket_spin_lock look identical for large and small number of cpus. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/9eea42d16aabc7624488eb62213a763dbbacef38.1308878118.git.jeremy.fitzhardinge@citrix.com Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/spinlock.h | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index f8d51dc36366..078319e3d0c0 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 */ } -- 2.39.5