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linux-next/lib/atomic64.c
Peter Zijlstra 560cb12a40 locking,arch: Rewrite generic atomic support
Rewrite generic atomic support to only require cmpxchg(), generate all
other primitives from that.

Furthermore reduce the endless repetition for all these primitives to
a few CPP macros. This way we get more for less lines.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140508135852.940119622@infradead.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-arch@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-08-14 12:48:14 +02:00

169 lines
4.1 KiB
C

/*
* 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 <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 {
raw_spinlock_t lock;
char pad[L1_CACHE_BYTES];
} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
[0 ... (NR_LOCKS - 1)] = {
.lock = __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
},
};
static inline raw_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;
raw_spinlock_t *lock = lock_addr(v);
long long val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(atomic64_read);
void atomic64_set(atomic64_t *v, long long i)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
raw_spin_lock_irqsave(lock, flags);
v->counter = i;
raw_spin_unlock_irqrestore(lock, flags);
}
EXPORT_SYMBOL(atomic64_set);
#define ATOMIC64_OP(op, c_op) \
void atomic64_##op(long long a, atomic64_t *v) \
{ \
unsigned long flags; \
raw_spinlock_t *lock = lock_addr(v); \
\
raw_spin_lock_irqsave(lock, flags); \
v->counter c_op a; \
raw_spin_unlock_irqrestore(lock, flags); \
} \
EXPORT_SYMBOL(atomic64_##op);
#define ATOMIC64_OP_RETURN(op, c_op) \
long long atomic64_##op##_return(long long a, atomic64_t *v) \
{ \
unsigned long flags; \
raw_spinlock_t *lock = lock_addr(v); \
long long val; \
\
raw_spin_lock_irqsave(lock, flags); \
val = (v->counter c_op a); \
raw_spin_unlock_irqrestore(lock, flags); \
return val; \
} \
EXPORT_SYMBOL(atomic64_##op##_return);
#define ATOMIC64_OPS(op, c_op) \
ATOMIC64_OP(op, c_op) \
ATOMIC64_OP_RETURN(op, c_op)
ATOMIC64_OPS(add, +=)
ATOMIC64_OPS(sub, -=)
#undef ATOMIC64_OPS
#undef ATOMIC64_OP_RETURN
#undef ATOMIC64_OP
long long atomic64_dec_if_positive(atomic64_t *v)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
long long val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter - 1;
if (val >= 0)
v->counter = val;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(atomic64_dec_if_positive);
long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
long long val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
if (val == o)
v->counter = n;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(atomic64_cmpxchg);
long long atomic64_xchg(atomic64_t *v, long long new)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
long long val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
v->counter = new;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(atomic64_xchg);
int atomic64_add_unless(atomic64_t *v, long long a, long long u)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
int ret = 0;
raw_spin_lock_irqsave(lock, flags);
if (v->counter != u) {
v->counter += a;
ret = 1;
}
raw_spin_unlock_irqrestore(lock, flags);
return ret;
}
EXPORT_SYMBOL(atomic64_add_unless);