From 84eb950db13ca40a0572ce9957e14723500943d6 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 2 Jul 2010 23:26:36 +0100 Subject: [PATCH] x86, ticketlock: Clean up types and accessors A few cleanups to the way spinlocks are defined and accessed: - define __ticket_t which is the size of a spinlock ticket (ie, enough bits to hold all the cpus) - Define struct arch_spinlock as a union containing plain slock and the head and tail tickets - Use head and tail to implement some of the spinlock predicates. - Make all ticket variables unsigned. - Use TICKET_SHIFT to form constants Most of this will be used in later patches. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/spinlock.h | 24 ++++++++++-------------- arch/x86/include/asm/spinlock_types.h | 20 ++++++++++++++++++-- 2 files changed, 28 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index ee67edf86fdd..ea2a04f69ca9 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -55,11 +55,9 @@ * much between them in performance though, especially as locks are out of line. */ #if (NR_CPUS < 256) -#define TICKET_SHIFT 8 - static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) { - short inc = 0x0100; + unsigned short inc = 1 << TICKET_SHIFT; asm volatile ( LOCK_PREFIX "xaddw %w0, %1\n" @@ -78,7 +76,7 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock) { - int tmp, new; + unsigned int tmp, new; asm volatile("movzwl %2, %0\n\t" "cmpb %h0,%b0\n\t" @@ -103,12 +101,10 @@ static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock) : "memory", "cc"); } #else -#define TICKET_SHIFT 16 - static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) { - int inc = 0x00010000; - int tmp; + unsigned inc = 1 << TICKET_SHIFT; + unsigned tmp; asm volatile(LOCK_PREFIX "xaddl %0, %1\n" "movzwl %w0, %2\n\t" @@ -128,8 +124,8 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock) static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock) { - int tmp; - int new; + unsigned tmp; + unsigned new; asm volatile("movl %2,%0\n\t" "movl %0,%1\n\t" @@ -159,16 +155,16 @@ static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock) static inline int __ticket_spin_is_locked(arch_spinlock_t *lock) { - int tmp = ACCESS_ONCE(lock->slock); + struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); - return !!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1 << TICKET_SHIFT) - 1)); + return !!(tmp.tail ^ tmp.head); } static inline int __ticket_spin_is_contended(arch_spinlock_t *lock) { - int tmp = ACCESS_ONCE(lock->slock); + struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); - return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1; + return ((tmp.tail - tmp.head) & TICKET_MASK) > 1; } #ifndef CONFIG_PARAVIRT_SPINLOCKS diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h index 7c7a486fcb68..1c51bd231e49 100644 --- a/arch/x86/include/asm/spinlock_types.h +++ b/arch/x86/include/asm/spinlock_types.h @@ -5,11 +5,27 @@ # error "please don't include this file directly" #endif +#include + +#if (CONFIG_NR_CPUS < 256) +typedef u8 __ticket_t; +#else +typedef u16 __ticket_t; +#endif + +#define TICKET_SHIFT (sizeof(__ticket_t) * 8) +#define TICKET_MASK ((__ticket_t)((1 << TICKET_SHIFT) - 1)) + typedef struct arch_spinlock { - unsigned int slock; + union { + unsigned int slock; + struct __raw_tickets { + __ticket_t head, tail; + } tickets; + }; } arch_spinlock_t; -#define __ARCH_SPIN_LOCK_UNLOCKED { 0 } +#define __ARCH_SPIN_LOCK_UNLOCKED { { .slock = 0 } } #include -- 2.20.1