arch/mips/include/asm/spinlock.h - kernel/bruno - Git at Google

 /*
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (C) 1999, 2000, 06 Ralf Baechle (ralf@linux-mips.org)
  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
  */
 #ifndef _ASM_SPINLOCK_H
 #define _ASM_SPINLOCK_H

 #include <linux/compiler.h>

 #include <asm/barrier.h>
 #include <asm/compiler.h>
 #include <asm/war.h>

 /*
  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  *
  * Simple spin lock operations.	 There are two variants, one clears IRQ's
  * on the local processor, one does not.
  *
  * These are fair FIFO ticket locks
  *
  * (the type definitions are in asm/spinlock_types.h)
  */


 /*
  * Ticket locks are conceptually two parts, one indicating the current head of
  * the queue, and the other indicating the current tail. The lock is acquired
  * by atomically noting the tail and incrementing it by one (thus adding
  * ourself to the queue and noting our position), then waiting until the head
  * becomes equal to the the initial value of the tail.
  */

 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
 {
 	u32 counters = ACCESS_ONCE(lock->lock);

 	return ((counters >> 16) ^ counters) & 0xffff;
 }

 static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
 	return lock.h.serving_now == lock.h.ticket;
 }

 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
 #define arch_spin_unlock_wait(x) \
 	while (arch_spin_is_locked(x)) { cpu_relax(); }

 static inline int arch_spin_is_contended(arch_spinlock_t *lock)
 {
 	u32 counters = ACCESS_ONCE(lock->lock);

 	return (((counters >> 16) - counters) & 0xffff) > 1;
 }
 #define arch_spin_is_contended	arch_spin_is_contended

 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
 	int my_ticket;
 	int tmp;
 	int inc = 0x10000;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__ (
 		"	.set push		# arch_spin_lock	\n"
 		"	.set noreorder					\n"
 		"							\n"
 		"1:	ll	%[ticket], %[ticket_ptr]		\n"
 		"	addu	%[my_ticket], %[ticket], %[inc]		\n"
 		"	sc	%[my_ticket], %[ticket_ptr]		\n"
 		"	beqzl	%[my_ticket], 1b			\n"
 		"	 nop						\n"
 		"	srl	%[my_ticket], %[ticket], 16		\n"
 		"	andi	%[ticket], %[ticket], 0xffff		\n"
 		"	bne	%[ticket], %[my_ticket], 4f		\n"
 		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
 		"2:							\n"
 		"	.subsection 2					\n"
 		"4:	andi	%[ticket], %[ticket], 0xffff		\n"
 		"	sll	%[ticket], 5				\n"
 		"							\n"
 		"6:	bnez	%[ticket], 6b				\n"
 		"	 subu	%[ticket], 1				\n"
 		"							\n"
 		"	lhu	%[ticket], %[serving_now_ptr]		\n"
 		"	beq	%[ticket], %[my_ticket], 2b		\n"
 		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
 		"	b	4b					\n"
 		"	 subu	%[ticket], %[ticket], 1			\n"
 		"	.previous					\n"
 		"	.set pop					\n"
 		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
 		  [serving_now_ptr] "+m" (lock->h.serving_now),
 		  [ticket] "=&r" (tmp),
 		  [my_ticket] "=&r" (my_ticket)
 		: [inc] "r" (inc));
 	} else {
 		__asm__ __volatile__ (
 		"	.set push		# arch_spin_lock	\n"
 		"	.set noreorder					\n"
 		"							\n"
 		"1:	ll	%[ticket], %[ticket_ptr]		\n"
 		"	addu	%[my_ticket], %[ticket], %[inc]		\n"
 		"	sc	%[my_ticket], %[ticket_ptr]		\n"
 		"	beqz	%[my_ticket], 1b			\n"
 		"	 srl	%[my_ticket], %[ticket], 16		\n"
 		"	andi	%[ticket], %[ticket], 0xffff		\n"
 		"	bne	%[ticket], %[my_ticket], 4f		\n"
 		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
 		"2:							\n"
 		"	.subsection 2					\n"
 		"4:	andi	%[ticket], %[ticket], 0xffff		\n"
 		"	sll	%[ticket], 5				\n"
 		"							\n"
 		"6:	bnez	%[ticket], 6b				\n"
 		"	 subu	%[ticket], 1				\n"
 		"							\n"
 		"	lhu	%[ticket], %[serving_now_ptr]		\n"
 		"	beq	%[ticket], %[my_ticket], 2b		\n"
 		"	 subu	%[ticket], %[my_ticket], %[ticket]	\n"
 		"	b	4b					\n"
 		"	 subu	%[ticket], %[ticket], 1			\n"
 		"	.previous					\n"
 		"	.set pop					\n"
 		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
 		  [serving_now_ptr] "+m" (lock->h.serving_now),
 		  [ticket] "=&r" (tmp),
 		  [my_ticket] "=&r" (my_ticket)
 		: [inc] "r" (inc));
 	}

 	smp_llsc_mb();
 }

 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
 	unsigned int serving_now = lock->h.serving_now + 1;
 	wmb();
 	lock->h.serving_now = (u16)serving_now;
 	nudge_writes();
 }

 static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
 {
 	int tmp, tmp2, tmp3;
 	int inc = 0x10000;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__ (
 		"	.set push		# arch_spin_trylock	\n"
 		"	.set noreorder					\n"
 		"							\n"
 		"1:	ll	%[ticket], %[ticket_ptr]		\n"
 		"	srl	%[my_ticket], %[ticket], 16		\n"
 		"	andi	%[now_serving], %[ticket], 0xffff	\n"
 		"	bne	%[my_ticket], %[now_serving], 3f	\n"
 		"	 addu	%[ticket], %[ticket], %[inc]		\n"
 		"	sc	%[ticket], %[ticket_ptr]		\n"
 		"	beqzl	%[ticket], 1b				\n"
 		"	 li	%[ticket], 1				\n"
 		"2:							\n"
 		"	.subsection 2					\n"
 		"3:	b	2b					\n"
 		"	 li	%[ticket], 0				\n"
 		"	.previous					\n"
 		"	.set pop					\n"
 		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
 		  [ticket] "=&r" (tmp),
 		  [my_ticket] "=&r" (tmp2),
 		  [now_serving] "=&r" (tmp3)
 		: [inc] "r" (inc));
 	} else {
 		__asm__ __volatile__ (
 		"	.set push		# arch_spin_trylock	\n"
 		"	.set noreorder					\n"
 		"							\n"
 		"1:	ll	%[ticket], %[ticket_ptr]		\n"
 		"	srl	%[my_ticket], %[ticket], 16		\n"
 		"	andi	%[now_serving], %[ticket], 0xffff	\n"
 		"	bne	%[my_ticket], %[now_serving], 3f	\n"
 		"	 addu	%[ticket], %[ticket], %[inc]		\n"
 		"	sc	%[ticket], %[ticket_ptr]		\n"
 		"	beqz	%[ticket], 1b				\n"
 		"	 li	%[ticket], 1				\n"
 		"2:							\n"
 		"	.subsection 2					\n"
 		"3:	b	2b					\n"
 		"	 li	%[ticket], 0				\n"
 		"	.previous					\n"
 		"	.set pop					\n"
 		: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
 		  [ticket] "=&r" (tmp),
 		  [my_ticket] "=&r" (tmp2),
 		  [now_serving] "=&r" (tmp3)
 		: [inc] "r" (inc));
 	}

 	smp_llsc_mb();

 	return tmp;
 }

 /*
  * Read-write spinlocks, allowing multiple readers but only one writer.
  *
  * NOTE! it is quite common to have readers in interrupts but no interrupt
  * writers. For those circumstances we can "mix" irq-safe locks - any writer
  * needs to get a irq-safe write-lock, but readers can get non-irqsafe
  * read-locks.
  */

 /*
  * read_can_lock - would read_trylock() succeed?
  * @lock: the rwlock in question.
  */
 #define arch_read_can_lock(rw)	((rw)->lock >= 0)

 /*
  * write_can_lock - would write_trylock() succeed?
  * @lock: the rwlock in question.
  */
 #define arch_write_can_lock(rw) (!(rw)->lock)

 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__(
 		"	.set	noreorder	# arch_read_lock	\n"
 		"1:	ll	%1, %2					\n"
 		"	bltz	%1, 1b					\n"
 		"	 addu	%1, 1					\n"
 		"	sc	%1, %0					\n"
 		"	beqzl	%1, 1b					\n"
 		"	 nop						\n"
 		"	.set	reorder					\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	} else {
 		do {
 			__asm__ __volatile__(
 			"1:	ll	%1, %2	# arch_read_lock	\n"
 			"	bltz	%1, 1b				\n"
 			"	 addu	%1, 1				\n"
 			"2:	sc	%1, %0				\n"
 			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 			: GCC_OFF_SMALL_ASM() (rw->lock)
 			: "memory");
 		} while (unlikely(!tmp));
 	}

 	smp_llsc_mb();
 }

 static inline void arch_read_unlock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;

 	smp_mb__before_llsc();

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__(
 		"1:	ll	%1, %2		# arch_read_unlock	\n"
 		"	addiu	%1, -1					\n"
 		"	sc	%1, %0					\n"
 		"	beqzl	%1, 1b					\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	} else {
 		do {
 			__asm__ __volatile__(
 			"1:	ll	%1, %2	# arch_read_unlock	\n"
 			"	addiu	%1, -1				\n"
 			"	sc	%1, %0				\n"
 			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 			: GCC_OFF_SMALL_ASM() (rw->lock)
 			: "memory");
 		} while (unlikely(!tmp));
 	}
 }

 static inline void arch_write_lock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__(
 		"	.set	noreorder	# arch_write_lock	\n"
 		"1:	ll	%1, %2					\n"
 		"	bnez	%1, 1b					\n"
 		"	 lui	%1, 0x8000				\n"
 		"	sc	%1, %0					\n"
 		"	beqzl	%1, 1b					\n"
 		"	 nop						\n"
 		"	.set	reorder					\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	} else {
 		do {
 			__asm__ __volatile__(
 			"1:	ll	%1, %2	# arch_write_lock	\n"
 			"	bnez	%1, 1b				\n"
 			"	 lui	%1, 0x8000			\n"
 			"2:	sc	%1, %0				\n"
 			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
 			: GCC_OFF_SMALL_ASM() (rw->lock)
 			: "memory");
 		} while (unlikely(!tmp));
 	}

 	smp_llsc_mb();
 }

 static inline void arch_write_unlock(arch_rwlock_t *rw)
 {
 	smp_mb__before_llsc();

 	__asm__ __volatile__(
 	"				# arch_write_unlock	\n"
 	"	sw	$0, %0					\n"
 	: "=m" (rw->lock)
 	: "m" (rw->lock)
 	: "memory");
 }

 static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;
 	int ret;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__(
 		"	.set	noreorder	# arch_read_trylock	\n"
 		"	li	%2, 0					\n"
 		"1:	ll	%1, %3					\n"
 		"	bltz	%1, 2f					\n"
 		"	 addu	%1, 1					\n"
 		"	sc	%1, %0					\n"
 		"	.set	reorder					\n"
 		"	beqzl	%1, 1b					\n"
 		"	 nop						\n"
 		__WEAK_LLSC_MB
 		"	li	%2, 1					\n"
 		"2:							\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	} else {
 		__asm__ __volatile__(
 		"	.set	noreorder	# arch_read_trylock	\n"
 		"	li	%2, 0					\n"
 		"1:	ll	%1, %3					\n"
 		"	bltz	%1, 2f					\n"
 		"	 addu	%1, 1					\n"
 		"	sc	%1, %0					\n"
 		"	beqz	%1, 1b					\n"
 		"	 nop						\n"
 		"	.set	reorder					\n"
 		__WEAK_LLSC_MB
 		"	li	%2, 1					\n"
 		"2:							\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	}

 	return ret;
 }

 static inline int arch_write_trylock(arch_rwlock_t *rw)
 {
 	unsigned int tmp;
 	int ret;

 	if (R10000_LLSC_WAR) {
 		__asm__ __volatile__(
 		"	.set	noreorder	# arch_write_trylock	\n"
 		"	li	%2, 0					\n"
 		"1:	ll	%1, %3					\n"
 		"	bnez	%1, 2f					\n"
 		"	 lui	%1, 0x8000				\n"
 		"	sc	%1, %0					\n"
 		"	beqzl	%1, 1b					\n"
 		"	 nop						\n"
 		__WEAK_LLSC_MB
 		"	li	%2, 1					\n"
 		"	.set	reorder					\n"
 		"2:							\n"
 		: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
 		: GCC_OFF_SMALL_ASM() (rw->lock)
 		: "memory");
 	} else {
 		do {
 			__asm__ __volatile__(
 			"	ll	%1, %3	# arch_write_trylock	\n"
 			"	li	%2, 0				\n"
 			"	bnez	%1, 2f				\n"
 			"	lui	%1, 0x8000			\n"
 			"	sc	%1, %0				\n"
 			"	li	%2, 1				\n"
 			"2:						\n"
 			: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp),
 			  "=&r" (ret)
 			: GCC_OFF_SMALL_ASM() (rw->lock)
 			: "memory");
 		} while (unlikely(!tmp));

 		smp_llsc_mb();
 	}

 	return ret;
 }

 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

 #define arch_spin_relax(lock)	cpu_relax()
 #define arch_read_relax(lock)	cpu_relax()
 #define arch_write_relax(lock)	cpu_relax()

 #endif /* _ASM_SPINLOCK_H */
	/*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* Copyright (C) 1999, 2000, 06 Ralf Baechle (ralf@linux-mips.org)
	* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
	*/
	#ifndef _ASM_SPINLOCK_H
	#define _ASM_SPINLOCK_H

	#include <linux/compiler.h>

	#include <asm/barrier.h>
	#include <asm/compiler.h>
	#include <asm/war.h>

	/*
	* Your basic SMP spinlocks, allowing only a single CPU anywhere
	*
	* Simple spin lock operations. There are two variants, one clears IRQ's
	* on the local processor, one does not.
	*
	* These are fair FIFO ticket locks
	*
	* (the type definitions are in asm/spinlock_types.h)
	*/


	/*
	* Ticket locks are conceptually two parts, one indicating the current head of
	* the queue, and the other indicating the current tail. The lock is acquired
	* by atomically noting the tail and incrementing it by one (thus adding
	* ourself to the queue and noting our position), then waiting until the head
	* becomes equal to the the initial value of the tail.
	*/

	static inline int arch_spin_is_locked(arch_spinlock_t *lock)
	{
	u32 counters = ACCESS_ONCE(lock->lock);

	return ((counters >> 16) ^ counters) & 0xffff;
	}

	static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
	{
	return lock.h.serving_now == lock.h.ticket;
	}

	#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
	#define arch_spin_unlock_wait(x) \
	while (arch_spin_is_locked(x)) { cpu_relax(); }

	static inline int arch_spin_is_contended(arch_spinlock_t *lock)
	{
	u32 counters = ACCESS_ONCE(lock->lock);

	return (((counters >> 16) - counters) & 0xffff) > 1;
	}
	#define arch_spin_is_contended arch_spin_is_contended

	static inline void arch_spin_lock(arch_spinlock_t *lock)
	{
	int my_ticket;
	int tmp;
	int inc = 0x10000;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__ (
	" .set push # arch_spin_lock \n"
	" .set noreorder \n"
	" \n"
	"1: ll %[ticket], %[ticket_ptr] \n"
	" addu %[my_ticket], %[ticket], %[inc] \n"
	" sc %[my_ticket], %[ticket_ptr] \n"
	" beqzl %[my_ticket], 1b \n"
	" nop \n"
	" srl %[my_ticket], %[ticket], 16 \n"
	" andi %[ticket], %[ticket], 0xffff \n"
	" bne %[ticket], %[my_ticket], 4f \n"
	" subu %[ticket], %[my_ticket], %[ticket] \n"
	"2: \n"
	" .subsection 2 \n"
	"4: andi %[ticket], %[ticket], 0xffff \n"
	" sll %[ticket], 5 \n"
	" \n"
	"6: bnez %[ticket], 6b \n"
	" subu %[ticket], 1 \n"
	" \n"
	" lhu %[ticket], %[serving_now_ptr] \n"
	" beq %[ticket], %[my_ticket], 2b \n"
	" subu %[ticket], %[my_ticket], %[ticket] \n"
	" b 4b \n"
	" subu %[ticket], %[ticket], 1 \n"
	" .previous \n"
	" .set pop \n"
	: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
	[serving_now_ptr] "+m" (lock->h.serving_now),
	[ticket] "=&r" (tmp),
	[my_ticket] "=&r" (my_ticket)
	: [inc] "r" (inc));
	} else {
	__asm__ __volatile__ (
	" .set push # arch_spin_lock \n"
	" .set noreorder \n"
	" \n"
	"1: ll %[ticket], %[ticket_ptr] \n"
	" addu %[my_ticket], %[ticket], %[inc] \n"
	" sc %[my_ticket], %[ticket_ptr] \n"
	" beqz %[my_ticket], 1b \n"
	" srl %[my_ticket], %[ticket], 16 \n"
	" andi %[ticket], %[ticket], 0xffff \n"
	" bne %[ticket], %[my_ticket], 4f \n"
	" subu %[ticket], %[my_ticket], %[ticket] \n"
	"2: \n"
	" .subsection 2 \n"
	"4: andi %[ticket], %[ticket], 0xffff \n"
	" sll %[ticket], 5 \n"
	" \n"
	"6: bnez %[ticket], 6b \n"
	" subu %[ticket], 1 \n"
	" \n"
	" lhu %[ticket], %[serving_now_ptr] \n"
	" beq %[ticket], %[my_ticket], 2b \n"
	" subu %[ticket], %[my_ticket], %[ticket] \n"
	" b 4b \n"
	" subu %[ticket], %[ticket], 1 \n"
	" .previous \n"
	" .set pop \n"
	: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
	[serving_now_ptr] "+m" (lock->h.serving_now),
	[ticket] "=&r" (tmp),
	[my_ticket] "=&r" (my_ticket)
	: [inc] "r" (inc));
	}

	smp_llsc_mb();
	}

	static inline void arch_spin_unlock(arch_spinlock_t *lock)
	{
	unsigned int serving_now = lock->h.serving_now + 1;
	wmb();
	lock->h.serving_now = (u16)serving_now;
	nudge_writes();
	}

	static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
	{
	int tmp, tmp2, tmp3;
	int inc = 0x10000;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__ (
	" .set push # arch_spin_trylock \n"
	" .set noreorder \n"
	" \n"
	"1: ll %[ticket], %[ticket_ptr] \n"
	" srl %[my_ticket], %[ticket], 16 \n"
	" andi %[now_serving], %[ticket], 0xffff \n"
	" bne %[my_ticket], %[now_serving], 3f \n"
	" addu %[ticket], %[ticket], %[inc] \n"
	" sc %[ticket], %[ticket_ptr] \n"
	" beqzl %[ticket], 1b \n"
	" li %[ticket], 1 \n"
	"2: \n"
	" .subsection 2 \n"
	"3: b 2b \n"
	" li %[ticket], 0 \n"
	" .previous \n"
	" .set pop \n"
	: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
	[ticket] "=&r" (tmp),
	[my_ticket] "=&r" (tmp2),
	[now_serving] "=&r" (tmp3)
	: [inc] "r" (inc));
	} else {
	__asm__ __volatile__ (
	" .set push # arch_spin_trylock \n"
	" .set noreorder \n"
	" \n"
	"1: ll %[ticket], %[ticket_ptr] \n"
	" srl %[my_ticket], %[ticket], 16 \n"
	" andi %[now_serving], %[ticket], 0xffff \n"
	" bne %[my_ticket], %[now_serving], 3f \n"
	" addu %[ticket], %[ticket], %[inc] \n"
	" sc %[ticket], %[ticket_ptr] \n"
	" beqz %[ticket], 1b \n"
	" li %[ticket], 1 \n"
	"2: \n"
	" .subsection 2 \n"
	"3: b 2b \n"
	" li %[ticket], 0 \n"
	" .previous \n"
	" .set pop \n"
	: [ticket_ptr] "+" GCC_OFF_SMALL_ASM() (lock->lock),
	[ticket] "=&r" (tmp),
	[my_ticket] "=&r" (tmp2),
	[now_serving] "=&r" (tmp3)
	: [inc] "r" (inc));
	}

	smp_llsc_mb();

	return tmp;
	}

	/*
	* Read-write spinlocks, allowing multiple readers but only one writer.
	*
	* NOTE! it is quite common to have readers in interrupts but no interrupt
	* writers. For those circumstances we can "mix" irq-safe locks - any writer
	* needs to get a irq-safe write-lock, but readers can get non-irqsafe
	* read-locks.
	*/

	/*
	* read_can_lock - would read_trylock() succeed?
	* @lock: the rwlock in question.
	*/
	#define arch_read_can_lock(rw) ((rw)->lock >= 0)

	/*
	* write_can_lock - would write_trylock() succeed?
	* @lock: the rwlock in question.
	*/
	#define arch_write_can_lock(rw) (!(rw)->lock)

	static inline void arch_read_lock(arch_rwlock_t *rw)
	{
	unsigned int tmp;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__(
	" .set noreorder # arch_read_lock \n"
	"1: ll %1, %2 \n"
	" bltz %1, 1b \n"
	" addu %1, 1 \n"
	" sc %1, %0 \n"
	" beqzl %1, 1b \n"
	" nop \n"
	" .set reorder \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} else {
	do {
	__asm__ __volatile__(
	"1: ll %1, %2 # arch_read_lock \n"
	" bltz %1, 1b \n"
	" addu %1, 1 \n"
	"2: sc %1, %0 \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} while (unlikely(!tmp));
	}

	smp_llsc_mb();
	}

	static inline void arch_read_unlock(arch_rwlock_t *rw)
	{
	unsigned int tmp;

	smp_mb__before_llsc();

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__(
	"1: ll %1, %2 # arch_read_unlock \n"
	" addiu %1, -1 \n"
	" sc %1, %0 \n"
	" beqzl %1, 1b \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} else {
	do {
	__asm__ __volatile__(
	"1: ll %1, %2 # arch_read_unlock \n"
	" addiu %1, -1 \n"
	" sc %1, %0 \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} while (unlikely(!tmp));
	}
	}

	static inline void arch_write_lock(arch_rwlock_t *rw)
	{
	unsigned int tmp;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__(
	" .set noreorder # arch_write_lock \n"
	"1: ll %1, %2 \n"
	" bnez %1, 1b \n"
	" lui %1, 0x8000 \n"
	" sc %1, %0 \n"
	" beqzl %1, 1b \n"
	" nop \n"
	" .set reorder \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} else {
	do {
	__asm__ __volatile__(
	"1: ll %1, %2 # arch_write_lock \n"
	" bnez %1, 1b \n"
	" lui %1, 0x8000 \n"
	"2: sc %1, %0 \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} while (unlikely(!tmp));
	}

	smp_llsc_mb();
	}

	static inline void arch_write_unlock(arch_rwlock_t *rw)
	{
	smp_mb__before_llsc();

	__asm__ __volatile__(
	" # arch_write_unlock \n"
	" sw $0, %0 \n"
	: "=m" (rw->lock)
	: "m" (rw->lock)
	: "memory");
	}

	static inline int arch_read_trylock(arch_rwlock_t *rw)
	{
	unsigned int tmp;
	int ret;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__(
	" .set noreorder # arch_read_trylock \n"
	" li %2, 0 \n"
	"1: ll %1, %3 \n"
	" bltz %1, 2f \n"
	" addu %1, 1 \n"
	" sc %1, %0 \n"
	" .set reorder \n"
	" beqzl %1, 1b \n"
	" nop \n"
	__WEAK_LLSC_MB
	" li %2, 1 \n"
	"2: \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} else {
	__asm__ __volatile__(
	" .set noreorder # arch_read_trylock \n"
	" li %2, 0 \n"
	"1: ll %1, %3 \n"
	" bltz %1, 2f \n"
	" addu %1, 1 \n"
	" sc %1, %0 \n"
	" beqz %1, 1b \n"
	" nop \n"
	" .set reorder \n"
	__WEAK_LLSC_MB
	" li %2, 1 \n"
	"2: \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	}

	return ret;
	}

	static inline int arch_write_trylock(arch_rwlock_t *rw)
	{
	unsigned int tmp;
	int ret;

	if (R10000_LLSC_WAR) {
	__asm__ __volatile__(
	" .set noreorder # arch_write_trylock \n"
	" li %2, 0 \n"
	"1: ll %1, %3 \n"
	" bnez %1, 2f \n"
	" lui %1, 0x8000 \n"
	" sc %1, %0 \n"
	" beqzl %1, 1b \n"
	" nop \n"
	__WEAK_LLSC_MB
	" li %2, 1 \n"
	" .set reorder \n"
	"2: \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp), "=&r" (ret)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} else {
	do {
	__asm__ __volatile__(
	" ll %1, %3 # arch_write_trylock \n"
	" li %2, 0 \n"
	" bnez %1, 2f \n"
	" lui %1, 0x8000 \n"
	" sc %1, %0 \n"
	" li %2, 1 \n"
	"2: \n"
	: "=" GCC_OFF_SMALL_ASM() (rw->lock), "=&r" (tmp),
	"=&r" (ret)
	: GCC_OFF_SMALL_ASM() (rw->lock)
	: "memory");
	} while (unlikely(!tmp));

	smp_llsc_mb();
	}

	return ret;
	}

	#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
	#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

	#define arch_spin_relax(lock) cpu_relax()
	#define arch_read_relax(lock) cpu_relax()
	#define arch_write_relax(lock) cpu_relax()

	#endif /* _ASM_SPINLOCK_H */