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62e8a3258b
This patch makes sure that atomic_{read,set}() are at least
{READ,WRITE}_ONCE().
We already had the 'requirement' that atomic_read() should use
ACCESS_ONCE(), and most archs had this, but a few were lacking.
All are now converted to use READ_ONCE().
And, by a symmetry and general paranoia argument, upgrade atomic_set()
to use WRITE_ONCE().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: james.hogan@imgtec.com
Cc: linux-kernel@vger.kernel.org
Cc: oleg@redhat.com
Cc: will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
189 lines
4.2 KiB
C
189 lines
4.2 KiB
C
/*
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* Generic C implementation of atomic counter operations. Usable on
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* UP systems only. Do not include in machine independent code.
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*
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* Originally implemented for MN10300.
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#ifndef __ASM_GENERIC_ATOMIC_H
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#define __ASM_GENERIC_ATOMIC_H
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#include <asm/cmpxchg.h>
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#include <asm/barrier.h>
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/*
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* atomic_$op() - $op integer to atomic variable
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* @i: integer value to $op
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* @v: pointer to the atomic variable
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*
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* Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
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* smp_mb__{before,after}_atomic().
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*/
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/*
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* atomic_$op_return() - $op interer to atomic variable and returns the result
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* @i: integer value to $op
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* @v: pointer to the atomic variable
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*
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* Atomically $ops @i to @v. Does imply a full memory barrier.
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*/
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#ifdef CONFIG_SMP
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/* we can build all atomic primitives from cmpxchg */
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#define ATOMIC_OP(op, c_op) \
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static inline void atomic_##op(int i, atomic_t *v) \
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{ \
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int c, old; \
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\
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c = v->counter; \
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while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
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c = old; \
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}
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#define ATOMIC_OP_RETURN(op, c_op) \
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static inline int atomic_##op##_return(int i, atomic_t *v) \
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{ \
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int c, old; \
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\
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c = v->counter; \
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while ((old = cmpxchg(&v->counter, c, c c_op i)) != c) \
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c = old; \
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\
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return c c_op i; \
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}
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#else
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#include <linux/irqflags.h>
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#define ATOMIC_OP(op, c_op) \
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static inline void atomic_##op(int i, atomic_t *v) \
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{ \
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unsigned long flags; \
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\
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raw_local_irq_save(flags); \
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v->counter = v->counter c_op i; \
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raw_local_irq_restore(flags); \
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}
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#define ATOMIC_OP_RETURN(op, c_op) \
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static inline int atomic_##op##_return(int i, atomic_t *v) \
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{ \
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unsigned long flags; \
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int ret; \
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\
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raw_local_irq_save(flags); \
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ret = (v->counter = v->counter c_op i); \
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raw_local_irq_restore(flags); \
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\
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return ret; \
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}
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#endif /* CONFIG_SMP */
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#ifndef atomic_add_return
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ATOMIC_OP_RETURN(add, +)
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#endif
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#ifndef atomic_sub_return
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ATOMIC_OP_RETURN(sub, -)
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#endif
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#ifndef atomic_and
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ATOMIC_OP(and, &)
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#endif
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#ifndef atomic_or
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ATOMIC_OP(or, |)
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#endif
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#ifndef atomic_xor
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ATOMIC_OP(xor, ^)
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#endif
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#undef ATOMIC_OP_RETURN
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#undef ATOMIC_OP
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/*
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* Atomic operations that C can't guarantee us. Useful for
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* resource counting etc..
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*/
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#define ATOMIC_INIT(i) { (i) }
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/**
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* atomic_read - read atomic variable
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* @v: pointer of type atomic_t
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*
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* Atomically reads the value of @v.
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*/
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#ifndef atomic_read
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#define atomic_read(v) READ_ONCE((v)->counter)
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#endif
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/**
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* atomic_set - set atomic variable
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* @v: pointer of type atomic_t
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* @i: required value
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*
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* Atomically sets the value of @v to @i.
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*/
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#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
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#include <linux/irqflags.h>
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static inline int atomic_add_negative(int i, atomic_t *v)
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{
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return atomic_add_return(i, v) < 0;
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}
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static inline void atomic_add(int i, atomic_t *v)
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{
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atomic_add_return(i, v);
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}
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static inline void atomic_sub(int i, atomic_t *v)
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{
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atomic_sub_return(i, v);
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}
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static inline void atomic_inc(atomic_t *v)
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{
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atomic_add_return(1, v);
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}
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static inline void atomic_dec(atomic_t *v)
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{
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atomic_sub_return(1, v);
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}
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#define atomic_dec_return(v) atomic_sub_return(1, (v))
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#define atomic_inc_return(v) atomic_add_return(1, (v))
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#define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
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#define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
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#define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
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#define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
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#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
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static inline int __atomic_add_unless(atomic_t *v, int a, int u)
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{
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int c, old;
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c = atomic_read(v);
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while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
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c = old;
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return c;
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}
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#endif /* __ASM_GENERIC_ATOMIC_H */
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