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x86, ticketlock: Clean up types and accessors

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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 <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Jeremy Fitzhardinge 2010-07-02 23:26:36 +01:00 committed by H. Peter Anvin
parent 8b8bc2f731
commit 84eb950db1
2 changed files with 28 additions and 16 deletions
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24
arch/x86/include/asm/spinlock.h
View File

@ -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

20
arch/x86/include/asm/spinlock_types.h
View File

@ -5,11 +5,27 @@
# error "please don't include this file directly"
#endif
#include <linux/types.h>
#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 <asm/rwlock.h>