linux-stable/lib/atomic64.c
Mark Rutland 1bdadf46ef locking/atomic: atomic64: support ARCH_ATOMIC
We'd like all architectures to convert to ARCH_ATOMIC, as this will
enable functionality, and once all architectures are converted it will
be possible to make significant cleanups to the atomic headers.

A number of architectures use asm-generic/atomic64.h, and it's
impractical to convert the header and all these architectures in one go.
To make it possible to convert them one-by-one, let's make the
asm-generic implementation function as either atomic64_*() or
arch_atomic64_*() depending on whether ARCH_ATOMIC is selected. To do
this, the generic implementations are prefixed as generic_atomic64_*(),
and preprocessor definitions map atomic64_*()/arch_atomic64_*() onto
these as appropriate.

Once all users are moved over to ARCH_ATOMIC the ifdeffery in the header
can be simplified and/or removed entirely.

For existing users (none of which select ARCH_ATOMIC), there should be
no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210525140232.53872-11-mark.rutland@arm.com
2021-05-26 13:20:50 +02:00

191 lines
4.6 KiB
C

// 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 {
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;
}
s64 generic_atomic64_read(const atomic64_t *v)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
s64 val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(generic_atomic64_read);
void generic_atomic64_set(atomic64_t *v, s64 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(generic_atomic64_set);
#define ATOMIC64_OP(op, c_op) \
void generic_atomic64_##op(s64 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(generic_atomic64_##op);
#define ATOMIC64_OP_RETURN(op, c_op) \
s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v) \
{ \
unsigned long flags; \
raw_spinlock_t *lock = lock_addr(v); \
s64 val; \
\
raw_spin_lock_irqsave(lock, flags); \
val = (v->counter c_op a); \
raw_spin_unlock_irqrestore(lock, 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; \
raw_spinlock_t *lock = lock_addr(v); \
s64 val; \
\
raw_spin_lock_irqsave(lock, flags); \
val = v->counter; \
v->counter c_op a; \
raw_spin_unlock_irqrestore(lock, 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_OP_RETURN(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_RETURN
#undef ATOMIC64_OP
s64 generic_atomic64_dec_if_positive(atomic64_t *v)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
s64 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(generic_atomic64_dec_if_positive);
s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
s64 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(generic_atomic64_cmpxchg);
s64 generic_atomic64_xchg(atomic64_t *v, s64 new)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
s64 val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
v->counter = new;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(generic_atomic64_xchg);
s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
{
unsigned long flags;
raw_spinlock_t *lock = lock_addr(v);
s64 val;
raw_spin_lock_irqsave(lock, flags);
val = v->counter;
if (val != u)
v->counter += a;
raw_spin_unlock_irqrestore(lock, flags);
return val;
}
EXPORT_SYMBOL(generic_atomic64_fetch_add_unless);