// SPDX-License-Identifier: GPL-2.0-or-later/* * Generic implementation of 64-bit atomics using spinlocks, * useful on processors that don't have 64-bit atomic instructions. * * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com> */#include <linux/types.h>#include <linux/cache.h>#include <linux/spinlock.h>#include <linux/init.h>#include <linux/export.h>#include <linux/atomic.h> /* * We use a hashed array of spinlocks to provide exclusive access * to each atomic64_t variable.  Since this is expected to used on * systems with small numbers of CPUs (<= 4 or so), we use a * relatively small array of 16 spinlocks to avoid wasting too much * memory on the spinlock array. */#define NR_LOCKS	16 /* * Ensure each lock is in a separate cacheline. */static union {	arch_spinlock_t lock;	char pad[L1_CACHE_BYTES];} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {	[0 ... (NR_LOCKS - 1)] = {		.lock =  __ARCH_SPIN_LOCK_UNLOCKED,	},}; static inline arch_spinlock_t *lock_addr(const atomic64_t *v){	unsigned long addr = (unsigned long) v; 	addr >>= L1_CACHE_SHIFT;	addr ^= (addr >> 8) ^ (addr >> 16);	return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;} s64 generic_atomic64_read(const atomic64_t *v){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v);	s64 val; 	local_irq_save(flags);	arch_spin_lock(lock);	val = v->counter;	arch_spin_unlock(lock);	local_irq_restore(flags);	return val;}EXPORT_SYMBOL(generic_atomic64_read); void generic_atomic64_set(atomic64_t *v, s64 i){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v); 	local_irq_save(flags);	arch_spin_lock(lock);	v->counter = i;	arch_spin_unlock(lock);	local_irq_restore(flags);}EXPORT_SYMBOL(generic_atomic64_set); #define ATOMIC64_OP(op, c_op)						\void generic_atomic64_##op(s64 a, atomic64_t *v)			\{									\	unsigned long flags;						\	arch_spinlock_t *lock = lock_addr(v);				\									\	local_irq_save(flags);						\	arch_spin_lock(lock);						\	v->counter c_op a;						\	arch_spin_unlock(lock);						\	local_irq_restore(flags);					\}									\EXPORT_SYMBOL(generic_atomic64_##op); #define ATOMIC64_OP_RETURN(op, c_op)					\s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v)		\{									\	unsigned long flags;						\	arch_spinlock_t *lock = lock_addr(v);				\	s64 val;							\									\	local_irq_save(flags);						\	arch_spin_lock(lock);						\	val = (v->counter c_op a);					\	arch_spin_unlock(lock);						\	local_irq_restore(flags);					\	return val;							\}									\EXPORT_SYMBOL(generic_atomic64_##op##_return); #define ATOMIC64_FETCH_OP(op, c_op)					\s64 generic_atomic64_fetch_##op(s64 a, atomic64_t *v)			\{									\	unsigned long flags;						\	arch_spinlock_t *lock = lock_addr(v);				\	s64 val;							\									\	local_irq_save(flags);						\	arch_spin_lock(lock);						\	val = v->counter;						\	v->counter c_op a;						\	arch_spin_unlock(lock);						\	local_irq_restore(flags);					\	return val;							\}									\EXPORT_SYMBOL(generic_atomic64_fetch_##op); #define ATOMIC64_OPS(op, c_op)						\	ATOMIC64_OP(op, c_op)						\	ATOMIC64_OP_RETURN(op, c_op)					\	ATOMIC64_FETCH_OP(op, c_op) ATOMIC64_OPS(add, +=)ATOMIC64_OPS(sub, -=) #undef ATOMIC64_OPS#define ATOMIC64_OPS(op, c_op)						\	ATOMIC64_OP(op, c_op)						\	ATOMIC64_FETCH_OP(op, c_op) ATOMIC64_OPS(and, &=)ATOMIC64_OPS(or, |=)ATOMIC64_OPS(xor, ^=) #undef ATOMIC64_OPS#undef ATOMIC64_FETCH_OP#undef ATOMIC64_OP s64 generic_atomic64_dec_if_positive(atomic64_t *v){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v);	s64 val; 	local_irq_save(flags);	arch_spin_lock(lock);	val = v->counter - 1;	if (val >= 0)		v->counter = val;	arch_spin_unlock(lock);	local_irq_restore(flags);	return val;}EXPORT_SYMBOL(generic_atomic64_dec_if_positive); s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v);	s64 val; 	local_irq_save(flags);	arch_spin_lock(lock);	val = v->counter;	if (val == o)		v->counter = n;	arch_spin_unlock(lock);	local_irq_restore(flags);	return val;}EXPORT_SYMBOL(generic_atomic64_cmpxchg); s64 generic_atomic64_xchg(atomic64_t *v, s64 new){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v);	s64 val; 	local_irq_save(flags);	arch_spin_lock(lock);	val = v->counter;	v->counter = new;	arch_spin_unlock(lock);	local_irq_restore(flags);	return val;}EXPORT_SYMBOL(generic_atomic64_xchg); s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u){	unsigned long flags;	arch_spinlock_t *lock = lock_addr(v);	s64 val; 	local_irq_save(flags);	arch_spin_lock(lock);	val = v->counter;	if (val != u)		v->counter += a;	arch_spin_unlock(lock);	local_irq_restore(flags); 	return val;}EXPORT_SYMBOL(generic_atomic64_fetch_add_unless);