e78fdfef84
This is to workaround the llock/scond livelock HS38x4 could get into a LLOCK/SCOND livelock in case of multiple overlapping coherency transactions in the SCU. The exclusive line state keeps rotating among contenting cores leading to a never ending cycle. So break the cycle by deferring the retry of failed exclusive access (SCOND). The actual delay needed is function of number of contending cores as well as the unrelated coherency traffic from other cores. To keep the code simple, start off with small delay of 1 which would suffice most cases and in case of contention double the delay. Eventually the delay is sufficient such that the coherency pipeline is drained, thus a subsequent exclusive access would succeed. Link: http://lkml.kernel.org/r/1438612568-28265-1-git-send-email-vgupta@synopsys.com Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
235 lines
6.0 KiB
C
235 lines
6.0 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _ASM_ARC_ATOMIC_H
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#define _ASM_ARC_ATOMIC_H
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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#include <linux/compiler.h>
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#include <asm/cmpxchg.h>
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#include <asm/barrier.h>
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#include <asm/smp.h>
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#define atomic_read(v) ((v)->counter)
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#ifdef CONFIG_ARC_HAS_LLSC
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#define atomic_set(v, i) (((v)->counter) = (i))
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#ifdef CONFIG_ARC_STAR_9000923308
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#define SCOND_FAIL_RETRY_VAR_DEF \
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unsigned int delay = 1, tmp; \
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#define SCOND_FAIL_RETRY_ASM \
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" bz 4f \n" \
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" ; --- scond fail delay --- \n" \
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" mov %[tmp], %[delay] \n" /* tmp = delay */ \
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"2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \
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" sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \
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" asl.f %[delay], %[delay], 1 \n" /* delay *= 2 */ \
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" mov.z %[delay], 1 \n" /* handle overflow */ \
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" b 1b \n" /* start over */ \
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"4: ; --- success --- \n" \
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#define SCOND_FAIL_RETRY_VARS \
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,[delay] "+&r" (delay),[tmp] "=&r" (tmp) \
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#else /* !CONFIG_ARC_STAR_9000923308 */
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#define SCOND_FAIL_RETRY_VAR_DEF
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#define SCOND_FAIL_RETRY_ASM \
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" bnz 1b \n" \
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#define SCOND_FAIL_RETRY_VARS
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#endif
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#define ATOMIC_OP(op, c_op, asm_op) \
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static inline void atomic_##op(int i, atomic_t *v) \
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{ \
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unsigned int val; \
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SCOND_FAIL_RETRY_VAR_DEF \
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\
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__asm__ __volatile__( \
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"1: llock %[val], [%[ctr]] \n" \
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" " #asm_op " %[val], %[val], %[i] \n" \
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" scond %[val], [%[ctr]] \n" \
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" \n" \
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SCOND_FAIL_RETRY_ASM \
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\
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: [val] "=&r" (val) /* Early clobber to prevent reg reuse */ \
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SCOND_FAIL_RETRY_VARS \
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: [ctr] "r" (&v->counter), /* Not "m": llock only supports reg direct addr mode */ \
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[i] "ir" (i) \
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: "cc"); \
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} \
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#define ATOMIC_OP_RETURN(op, c_op, asm_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 int val; \
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SCOND_FAIL_RETRY_VAR_DEF \
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\
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/* \
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* Explicit full memory barrier needed before/after as \
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* LLOCK/SCOND thmeselves don't provide any such semantics \
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*/ \
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smp_mb(); \
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\
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__asm__ __volatile__( \
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"1: llock %[val], [%[ctr]] \n" \
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" " #asm_op " %[val], %[val], %[i] \n" \
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" scond %[val], [%[ctr]] \n" \
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" \n" \
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SCOND_FAIL_RETRY_ASM \
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\
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: [val] "=&r" (val) \
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SCOND_FAIL_RETRY_VARS \
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: [ctr] "r" (&v->counter), \
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[i] "ir" (i) \
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: "cc"); \
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\
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smp_mb(); \
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\
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return val; \
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}
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#else /* !CONFIG_ARC_HAS_LLSC */
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#ifndef CONFIG_SMP
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/* violating atomic_xxx API locking protocol in UP for optimization sake */
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#define atomic_set(v, i) (((v)->counter) = (i))
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#else
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static inline void atomic_set(atomic_t *v, int i)
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{
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/*
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* Independent of hardware support, all of the atomic_xxx() APIs need
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* to follow the same locking rules to make sure that a "hardware"
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* atomic insn (e.g. LD) doesn't clobber an "emulated" atomic insn
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* sequence
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*
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* Thus atomic_set() despite being 1 insn (and seemingly atomic)
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* requires the locking.
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*/
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unsigned long flags;
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atomic_ops_lock(flags);
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v->counter = i;
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atomic_ops_unlock(flags);
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}
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#endif
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/*
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* Non hardware assisted Atomic-R-M-W
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* Locking would change to irq-disabling only (UP) and spinlocks (SMP)
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*/
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#define ATOMIC_OP(op, c_op, asm_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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atomic_ops_lock(flags); \
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v->counter c_op i; \
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atomic_ops_unlock(flags); \
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}
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#define ATOMIC_OP_RETURN(op, c_op, asm_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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unsigned long temp; \
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\
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/* \
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* spin lock/unlock provides the needed smp_mb() before/after \
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*/ \
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atomic_ops_lock(flags); \
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temp = v->counter; \
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temp c_op i; \
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v->counter = temp; \
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atomic_ops_unlock(flags); \
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\
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return temp; \
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}
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#endif /* !CONFIG_ARC_HAS_LLSC */
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#define ATOMIC_OPS(op, c_op, asm_op) \
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ATOMIC_OP(op, c_op, asm_op) \
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ATOMIC_OP_RETURN(op, c_op, asm_op)
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ATOMIC_OPS(add, +=, add)
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ATOMIC_OPS(sub, -=, sub)
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ATOMIC_OP(and, &=, and)
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#define atomic_clear_mask(mask, v) atomic_and(~(mask), (v))
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#undef ATOMIC_OPS
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#undef ATOMIC_OP_RETURN
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#undef ATOMIC_OP
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#undef SCOND_FAIL_RETRY_VAR_DEF
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#undef SCOND_FAIL_RETRY_ASM
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#undef SCOND_FAIL_RETRY_VARS
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/**
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* __atomic_add_unless - add unless the number is a given value
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* @v: pointer of type atomic_t
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* @a: the amount to add to v...
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* @u: ...unless v is equal to u.
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*
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* Atomically adds @a to @v, so long as it was not @u.
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* Returns the old value of @v
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*/
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#define __atomic_add_unless(v, a, u) \
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({ \
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int c, old; \
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\
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/* \
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* Explicit full memory barrier needed before/after as \
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* LLOCK/SCOND thmeselves don't provide any such semantics \
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*/ \
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smp_mb(); \
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\
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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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\
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smp_mb(); \
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\
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c; \
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})
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#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
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#define atomic_inc(v) atomic_add(1, v)
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#define atomic_dec(v) atomic_sub(1, v)
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#define atomic_inc_and_test(v) (atomic_add_return(1, v) == 0)
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#define atomic_dec_and_test(v) (atomic_sub_return(1, v) == 0)
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#define atomic_inc_return(v) atomic_add_return(1, (v))
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#define atomic_dec_return(v) atomic_sub_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_add_negative(i, v) (atomic_add_return(i, v) < 0)
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#define ATOMIC_INIT(i) { (i) }
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#include <asm-generic/atomic64.h>
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#endif
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#endif
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