arch/arc/include/asm/spinlock.h - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #ifndef __ASM_SPINLOCK_H
 #define __ASM_SPINLOCK_H

 #include <asm/spinlock_types.h>
 #include <asm/processor.h>
 #include <asm/barrier.h>

 #define arch_spin_is_locked(x)	((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
 #define arch_spin_lock_flags(lock, flags)	arch_spin_lock(lock)

 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
 {
 	smp_cond_load_acquire(&lock->slock, !VAL);
 }

 #ifdef CONFIG_ARC_HAS_LLSC

 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
 	unsigned int val;

 	smp_mb();

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[slock]]	\n"
 	"	breq	%[val], %[LOCKED], 1b	\n"	/* spin while LOCKED */
 	"	scond	%[LOCKED], [%[slock]]	\n"	/* acquire */
 	"	bnz	1b			\n"
 	"					\n"
 	: [val]		"=&r"	(val)
 	: [slock]	"r"	(&(lock->slock)),
 	  [LOCKED]	"r"	(__ARCH_SPIN_LOCK_LOCKED__)
 	: "memory", "cc");

 	smp_mb();
 }

 /* 1 - lock taken successfully */
 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned int val, got_it = 0;

 	smp_mb();

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[slock]]	\n"
 	"	breq	%[val], %[LOCKED], 4f	\n"	/* already LOCKED, just bail */
 	"	scond	%[LOCKED], [%[slock]]	\n"	/* acquire */
 	"	bnz	1b			\n"
 	"	mov	%[got_it], 1		\n"
 	"4:					\n"
 	"					\n"
 	: [val]		"=&r"	(val),
 	  [got_it]	"+&r"	(got_it)
 	: [slock]	"r"	(&(lock->slock)),
 	  [LOCKED]	"r"	(__ARCH_SPIN_LOCK_LOCKED__)
 	: "memory", "cc");

 	smp_mb();

 	return got_it;
 }

 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
 	smp_mb();

 	lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;

 	smp_mb();
 }

 /*
  * Read-write spinlocks, allowing multiple readers but only one writer.
  * Unfair locking as Writers could be starved indefinitely by Reader(s)
  */

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

 	smp_mb();

 	/*
 	 * zero means writer holds the lock exclusively, deny Reader.
 	 * Otherwise grant lock to first/subseq reader
 	 *
 	 * 	if (rw->counter > 0) {
 	 *		rw->counter--;
 	 *		ret = 1;
 	 *	}
 	 */

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[rwlock]]	\n"
 	"	brls	%[val], %[WR_LOCKED], 1b\n"	/* <= 0: spin while write locked */
 	"	sub	%[val], %[val], 1	\n"	/* reader lock */
 	"	scond	%[val], [%[rwlock]]	\n"
 	"	bnz	1b			\n"
 	"					\n"
 	: [val]		"=&r"	(val)
 	: [rwlock]	"r"	(&(rw->counter)),
 	  [WR_LOCKED]	"ir"	(0)
 	: "memory", "cc");

 	smp_mb();
 }

 /* 1 - lock taken successfully */
 static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
 	unsigned int val, got_it = 0;

 	smp_mb();

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[rwlock]]	\n"
 	"	brls	%[val], %[WR_LOCKED], 4f\n"	/* <= 0: already write locked, bail */
 	"	sub	%[val], %[val], 1	\n"	/* counter-- */
 	"	scond	%[val], [%[rwlock]]	\n"
 	"	bnz	1b			\n"	/* retry if collided with someone */
 	"	mov	%[got_it], 1		\n"
 	"					\n"
 	"4: ; --- done ---			\n"

 	: [val]		"=&r"	(val),
 	  [got_it]	"+&r"	(got_it)
 	: [rwlock]	"r"	(&(rw->counter)),
 	  [WR_LOCKED]	"ir"	(0)
 	: "memory", "cc");

 	smp_mb();

 	return got_it;
 }

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

 	smp_mb();

 	/*
 	 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
 	 * deny writer. Otherwise if unlocked grant to writer
 	 * Hence the claim that Linux rwlocks are unfair to writers.
 	 * (can be starved for an indefinite time by readers).
 	 *
 	 *	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
 	 *		rw->counter = 0;
 	 *		ret = 1;
 	 *	}
 	 */

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[rwlock]]	\n"
 	"	brne	%[val], %[UNLOCKED], 1b	\n"	/* while !UNLOCKED spin */
 	"	mov	%[val], %[WR_LOCKED]	\n"
 	"	scond	%[val], [%[rwlock]]	\n"
 	"	bnz	1b			\n"
 	"					\n"
 	: [val]		"=&r"	(val)
 	: [rwlock]	"r"	(&(rw->counter)),
 	  [UNLOCKED]	"ir"	(__ARCH_RW_LOCK_UNLOCKED__),
 	  [WR_LOCKED]	"ir"	(0)
 	: "memory", "cc");

 	smp_mb();
 }

 /* 1 - lock taken successfully */
 static inline int arch_write_trylock(arch_rwlock_t *rw)
 {
 	unsigned int val, got_it = 0;

 	smp_mb();

 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[rwlock]]	\n"
 	"	brne	%[val], %[UNLOCKED], 4f	\n"	/* !UNLOCKED, bail */
 	"	mov	%[val], %[WR_LOCKED]	\n"
 	"	scond	%[val], [%[rwlock]]	\n"
 	"	bnz	1b			\n"	/* retry if collided with someone */
 	"	mov	%[got_it], 1		\n"
 	"					\n"
 	"4: ; --- done ---			\n"

 	: [val]		"=&r"	(val),
 	  [got_it]	"+&r"	(got_it)
 	: [rwlock]	"r"	(&(rw->counter)),
 	  [UNLOCKED]	"ir"	(__ARCH_RW_LOCK_UNLOCKED__),
 	  [WR_LOCKED]	"ir"	(0)
 	: "memory", "cc");

 	smp_mb();

 	return got_it;
 }

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

 	smp_mb();

 	/*
 	 * rw->counter++;
 	 */
 	__asm__ __volatile__(
 	"1:	llock	%[val], [%[rwlock]]	\n"
 	"	add	%[val], %[val], 1	\n"
 	"	scond	%[val], [%[rwlock]]	\n"
 	"	bnz	1b			\n"
 	"					\n"
 	: [val]		"=&r"	(val)
 	: [rwlock]	"r"	(&(rw->counter))
 	: "memory", "cc");

 	smp_mb();
 }

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

 	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;

 	smp_mb();
 }

 #else	/* !CONFIG_ARC_HAS_LLSC */

 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
 	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

 	/*
 	 * This smp_mb() is technically superfluous, we only need the one
 	 * after the lock for providing the ACQUIRE semantics.
 	 * However doing the "right" thing was regressing hackbench
 	 * so keeping this, pending further investigation
 	 */
 	smp_mb();

 	__asm__ __volatile__(
 	"1:	ex  %0, [%1]		\n"
 	"	breq  %0, %2, 1b	\n"
 	: "+&r" (val)
 	: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
 	: "memory");

 	/*
 	 * ACQUIRE barrier to ensure load/store after taking the lock
 	 * don't "bleed-up" out of the critical section (leak-in is allowed)
 	 * http://www.spinics.net/lists/kernel/msg2010409.html
 	 *
 	 * ARCv2 only has load-load, store-store and all-all barrier
 	 * thus need the full all-all barrier
 	 */
 	smp_mb();
 }

 /* 1 - lock taken successfully */
 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

 	smp_mb();

 	__asm__ __volatile__(
 	"1:	ex  %0, [%1]		\n"
 	: "+r" (val)
 	: "r"(&(lock->slock))
 	: "memory");

 	smp_mb();

 	return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
 }

 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 {
 	unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;

 	/*
 	 * RELEASE barrier: given the instructions avail on ARCv2, full barrier
 	 * is the only option
 	 */
 	smp_mb();

 	__asm__ __volatile__(
 	"	ex  %0, [%1]		\n"
 	: "+r" (val)
 	: "r"(&(lock->slock))
 	: "memory");

 	/*
 	 * superfluous, but keeping for now - see pairing version in
 	 * arch_spin_lock above
 	 */
 	smp_mb();
 }

 /*
  * Read-write spinlocks, allowing multiple readers but only one writer.
  * Unfair locking as Writers could be starved indefinitely by Reader(s)
  *
  * The spinlock itself is contained in @counter and access to it is
  * serialized with @lock_mutex.
  */

 /* 1 - lock taken successfully */
 static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
 	int ret = 0;
 	unsigned long flags;

 	local_irq_save(flags);
 	arch_spin_lock(&(rw->lock_mutex));

 	/*
 	 * zero means writer holds the lock exclusively, deny Reader.
 	 * Otherwise grant lock to first/subseq reader
 	 */
 	if (rw->counter > 0) {
 		rw->counter--;
 		ret = 1;
 	}

 	arch_spin_unlock(&(rw->lock_mutex));
 	local_irq_restore(flags);

 	smp_mb();
 	return ret;
 }

 /* 1 - lock taken successfully */
 static inline int arch_write_trylock(arch_rwlock_t *rw)
 {
 	int ret = 0;
 	unsigned long flags;

 	local_irq_save(flags);
 	arch_spin_lock(&(rw->lock_mutex));

 	/*
 	 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
 	 * deny writer. Otherwise if unlocked grant to writer
 	 * Hence the claim that Linux rwlocks are unfair to writers.
 	 * (can be starved for an indefinite time by readers).
 	 */
 	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
 		rw->counter = 0;
 		ret = 1;
 	}
 	arch_spin_unlock(&(rw->lock_mutex));
 	local_irq_restore(flags);

 	return ret;
 }

 static inline void arch_read_lock(arch_rwlock_t *rw)
 {
 	while (!arch_read_trylock(rw))
 		cpu_relax();
 }

 static inline void arch_write_lock(arch_rwlock_t *rw)
 {
 	while (!arch_write_trylock(rw))
 		cpu_relax();
 }

 static inline void arch_read_unlock(arch_rwlock_t *rw)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	arch_spin_lock(&(rw->lock_mutex));
 	rw->counter++;
 	arch_spin_unlock(&(rw->lock_mutex));
 	local_irq_restore(flags);
 }

 static inline void arch_write_unlock(arch_rwlock_t *rw)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	arch_spin_lock(&(rw->lock_mutex));
 	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
 	arch_spin_unlock(&(rw->lock_mutex));
 	local_irq_restore(flags);
 }

 #endif

 #define arch_read_can_lock(x)	((x)->counter > 0)
 #define arch_write_can_lock(x)	((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)

 #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 */
	/*
	* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#ifndef __ASM_SPINLOCK_H
	#define __ASM_SPINLOCK_H

	#include <asm/spinlock_types.h>
	#include <asm/processor.h>
	#include <asm/barrier.h>

	#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
	#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

	static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
	{
	smp_cond_load_acquire(&lock->slock, !VAL);
	}

	#ifdef CONFIG_ARC_HAS_LLSC

	static inline void arch_spin_lock(arch_spinlock_t *lock)
	{
	unsigned int val;

	smp_mb();

	__asm__ __volatile__(
	"1: llock %[val], [%[slock]] \n"
	" breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */
	" scond %[LOCKED], [%[slock]] \n" /* acquire */
	" bnz 1b \n"
	" \n"
	: [val] "=&r" (val)
	: [slock] "r" (&(lock->slock)),
	[LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
	: "memory", "cc");

	smp_mb();
	}

	/* 1 - lock taken successfully */
	static inline int arch_spin_trylock(arch_spinlock_t *lock)
	{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1: llock %[val], [%[slock]] \n"
	" breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
	" scond %[LOCKED], [%[slock]] \n" /* acquire */
	" bnz 1b \n"
	" mov %[got_it], 1 \n"
	"4: \n"
	" \n"
	: [val] "=&r" (val),
	[got_it] "+&r" (got_it)
	: [slock] "r" (&(lock->slock)),
	[LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
	: "memory", "cc");

	smp_mb();

	return got_it;
	}

	static inline void arch_spin_unlock(arch_spinlock_t *lock)
	{
	smp_mb();

	lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;

	smp_mb();
	}

	/*
	* Read-write spinlocks, allowing multiple readers but only one writer.
	* Unfair locking as Writers could be starved indefinitely by Reader(s)
	*/

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

	smp_mb();

	/*
	* zero means writer holds the lock exclusively, deny Reader.
	* Otherwise grant lock to first/subseq reader
	*
	* if (rw->counter > 0) {
	* rw->counter--;
	* ret = 1;
	* }
	*/

	__asm__ __volatile__(
	"1: llock %[val], [%[rwlock]] \n"
	" brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */
	" sub %[val], %[val], 1 \n" /* reader lock */
	" scond %[val], [%[rwlock]] \n"
	" bnz 1b \n"
	" \n"
	: [val] "=&r" (val)
	: [rwlock] "r" (&(rw->counter)),
	[WR_LOCKED] "ir" (0)
	: "memory", "cc");

	smp_mb();
	}

	/* 1 - lock taken successfully */
	static inline int arch_read_trylock(arch_rwlock_t *rw)
	{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1: llock %[val], [%[rwlock]] \n"
	" brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
	" sub %[val], %[val], 1 \n" /* counter-- */
	" scond %[val], [%[rwlock]] \n"
	" bnz 1b \n" /* retry if collided with someone */
	" mov %[got_it], 1 \n"
	" \n"
	"4: ; --- done --- \n"

	: [val] "=&r" (val),
	[got_it] "+&r" (got_it)
	: [rwlock] "r" (&(rw->counter)),
	[WR_LOCKED] "ir" (0)
	: "memory", "cc");

	smp_mb();

	return got_it;
	}

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

	smp_mb();

	/*
	* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
	* deny writer. Otherwise if unlocked grant to writer
	* Hence the claim that Linux rwlocks are unfair to writers.
	* (can be starved for an indefinite time by readers).
	*
	* if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
	* rw->counter = 0;
	* ret = 1;
	* }
	*/

	__asm__ __volatile__(
	"1: llock %[val], [%[rwlock]] \n"
	" brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */
	" mov %[val], %[WR_LOCKED] \n"
	" scond %[val], [%[rwlock]] \n"
	" bnz 1b \n"
	" \n"
	: [val] "=&r" (val)
	: [rwlock] "r" (&(rw->counter)),
	[UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
	[WR_LOCKED] "ir" (0)
	: "memory", "cc");

	smp_mb();
	}

	/* 1 - lock taken successfully */
	static inline int arch_write_trylock(arch_rwlock_t *rw)
	{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1: llock %[val], [%[rwlock]] \n"
	" brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
	" mov %[val], %[WR_LOCKED] \n"
	" scond %[val], [%[rwlock]] \n"
	" bnz 1b \n" /* retry if collided with someone */
	" mov %[got_it], 1 \n"
	" \n"
	"4: ; --- done --- \n"

	: [val] "=&r" (val),
	[got_it] "+&r" (got_it)
	: [rwlock] "r" (&(rw->counter)),
	[UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
	[WR_LOCKED] "ir" (0)
	: "memory", "cc");

	smp_mb();

	return got_it;
	}

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

	smp_mb();

	/*
	* rw->counter++;
	*/
	__asm__ __volatile__(
	"1: llock %[val], [%[rwlock]] \n"
	" add %[val], %[val], 1 \n"
	" scond %[val], [%[rwlock]] \n"
	" bnz 1b \n"
	" \n"
	: [val] "=&r" (val)
	: [rwlock] "r" (&(rw->counter))
	: "memory", "cc");

	smp_mb();
	}

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

	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;

	smp_mb();
	}

	#else /* !CONFIG_ARC_HAS_LLSC */

	static inline void arch_spin_lock(arch_spinlock_t *lock)
	{
	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

	/*
	* This smp_mb() is technically superfluous, we only need the one
	* after the lock for providing the ACQUIRE semantics.
	* However doing the "right" thing was regressing hackbench
	* so keeping this, pending further investigation
	*/
	smp_mb();

	__asm__ __volatile__(
	"1: ex %0, [%1] \n"
	" breq %0, %2, 1b \n"
	: "+&r" (val)
	: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
	: "memory");

	/*
	* ACQUIRE barrier to ensure load/store after taking the lock
	* don't "bleed-up" out of the critical section (leak-in is allowed)
	* http://www.spinics.net/lists/kernel/msg2010409.html
	*
	* ARCv2 only has load-load, store-store and all-all barrier
	* thus need the full all-all barrier
	*/
	smp_mb();
	}

	/* 1 - lock taken successfully */
	static inline int arch_spin_trylock(arch_spinlock_t *lock)
	{
	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

	smp_mb();

	__asm__ __volatile__(
	"1: ex %0, [%1] \n"
	: "+r" (val)
	: "r"(&(lock->slock))
	: "memory");

	smp_mb();

	return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
	}

	static inline void arch_spin_unlock(arch_spinlock_t *lock)
	{
	unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;

	/*
	* RELEASE barrier: given the instructions avail on ARCv2, full barrier
	* is the only option
	*/
	smp_mb();

	__asm__ __volatile__(
	" ex %0, [%1] \n"
	: "+r" (val)
	: "r"(&(lock->slock))
	: "memory");

	/*
	* superfluous, but keeping for now - see pairing version in
	* arch_spin_lock above
	*/
	smp_mb();
	}

	/*
	* Read-write spinlocks, allowing multiple readers but only one writer.
	* Unfair locking as Writers could be starved indefinitely by Reader(s)
	*
	* The spinlock itself is contained in @counter and access to it is
	* serialized with @lock_mutex.
	*/

	/* 1 - lock taken successfully */
	static inline int arch_read_trylock(arch_rwlock_t *rw)
	{
	int ret = 0;
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));

	/*
	* zero means writer holds the lock exclusively, deny Reader.
	* Otherwise grant lock to first/subseq reader
	*/
	if (rw->counter > 0) {
	rw->counter--;
	ret = 1;
	}

	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);

	smp_mb();
	return ret;
	}

	/* 1 - lock taken successfully */
	static inline int arch_write_trylock(arch_rwlock_t *rw)
	{
	int ret = 0;
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));

	/*
	* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
	* deny writer. Otherwise if unlocked grant to writer
	* Hence the claim that Linux rwlocks are unfair to writers.
	* (can be starved for an indefinite time by readers).
	*/
	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
	rw->counter = 0;
	ret = 1;
	}
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);

	return ret;
	}

	static inline void arch_read_lock(arch_rwlock_t *rw)
	{
	while (!arch_read_trylock(rw))
	cpu_relax();
	}

	static inline void arch_write_lock(arch_rwlock_t *rw)
	{
	while (!arch_write_trylock(rw))
	cpu_relax();
	}

	static inline void arch_read_unlock(arch_rwlock_t *rw)
	{
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));
	rw->counter++;
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);
	}

	static inline void arch_write_unlock(arch_rwlock_t *rw)
	{
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));
	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);
	}

	#endif

	#define arch_read_can_lock(x) ((x)->counter > 0)
	#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)

	#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 */