Messages in this thread Patch in this message | | | From | Jeremy Fitzhardinge <> | Subject | [PATCH 11/12] x86/ticketlock: convert __ticket_spin_lock to use xadd() | Date | Wed, 24 Aug 2011 14:37:08 -0700 |
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From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Convert the two variants of __ticket_spin_lock() to use xadd(), which has the effect of making them identical, so remove the duplicate function.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/include/asm/spinlock.h | 35 +++++------------------------------ 1 files changed, 5 insertions(+), 30 deletions(-)
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 1c8a23c..adf010a 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -55,26 +55,22 @@ * save some instructions and make the code more elegant. There really isn't * much between them in performance though, especially as locks are out of line. */ -#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"); + inc = xadd(&lock->tickets, inc); for (;;) { - if (inc.tickets.head == inc.tickets.tail) + if (inc.head == inc.tail) break; cpu_relax(); - inc.tickets.head = ACCESS_ONCE(lock->tickets.head); + inc.head = ACCESS_ONCE(lock->tickets.head); } barrier(); /* make sure nothing creeps before the lock is taken */ } +#if (NR_CPUS < 256) static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock) { unsigned int tmp, new; @@ -102,27 +98,6 @@ static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock) : "memory", "cc"); } #else -static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) -{ - unsigned inc = 1 << TICKET_SHIFT; - __ticket_t tmp; - - asm volatile(LOCK_PREFIX "xaddl %0, %1\n\t" - : "+r" (inc), "+m" (lock->slock) - : : "memory", "cc"); - - tmp = inc; - inc >>= TICKET_SHIFT; - - for (;;) { - if ((__ticket_t)inc == tmp) - break; - cpu_relax(); - tmp = ACCESS_ONCE(lock->tickets.head); - } - barrier(); /* make sure nothing creeps before the lock is taken */ -} - static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock) { unsigned tmp; -- 1.7.6
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