/* * 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> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/types.h> #include <linux/cache.h> #include <linux/spinlock.h> #include <linux/init.h> #include <asm/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 { spinlock_t lock; char pad[L1_CACHE_BYTES]; } atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp; static inline 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; } long long atomic64_read(const atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter; spin_unlock_irqrestore(lock, flags); return val; } void atomic64_set(atomic64_t *v, long long i) { unsigned long flags; spinlock_t *lock = lock_addr(v); spin_lock_irqsave(lock, flags); v->counter = i; spin_unlock_irqrestore(lock, flags); } void atomic64_add(long long a, atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); spin_lock_irqsave(lock, flags); v->counter += a; spin_unlock_irqrestore(lock, flags); } long long atomic64_add_return(long long a, atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter += a; spin_unlock_irqrestore(lock, flags); return val; } void atomic64_sub(long long a, atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); spin_lock_irqsave(lock, flags); v->counter -= a; spin_unlock_irqrestore(lock, flags); } long long atomic64_sub_return(long long a, atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter -= a; spin_unlock_irqrestore(lock, flags); return val; } long long atomic64_dec_if_positive(atomic64_t *v) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter - 1; if (val >= 0) v->counter = val; spin_unlock_irqrestore(lock, flags); return val; } long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter; if (val == o) v->counter = n; spin_unlock_irqrestore(lock, flags); return val; } long long atomic64_xchg(atomic64_t *v, long long new) { unsigned long flags; spinlock_t *lock = lock_addr(v); long long val; spin_lock_irqsave(lock, flags); val = v->counter; v->counter = new; spin_unlock_irqrestore(lock, flags); return val; } int atomic64_add_unless(atomic64_t *v, long long a, long long u) { unsigned long flags; spinlock_t *lock = lock_addr(v); int ret = 1; spin_lock_irqsave(lock, flags); if (v->counter != u) { v->counter += a; ret = 0; } spin_unlock_irqrestore(lock, flags); return ret; } static int init_atomic64_lock(void) { int i; for (i = 0; i < NR_LOCKS; ++i) spin_lock_init(&atomic64_lock[i].lock); return 0; } pure_initcall(init_atomic64_lock);