Commit 84eb950d authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by H. Peter Anvin
Browse files

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: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 8b8bc2f7

arch/x86/include/asm/spinlock.h

+10 −14
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/spinlock_types.h

+18 −2
Original line number Diff line number Diff line
@@ -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 {

	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>

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