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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>
260 lines
6.2 KiB
C
260 lines
6.2 KiB
C
/*
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* include/asm-xtensa/atomic.h
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*
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* Atomic operations that C can't guarantee us. Useful for resource counting..
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2001 - 2008 Tensilica Inc.
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*/
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#ifndef _XTENSA_ATOMIC_H
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#define _XTENSA_ATOMIC_H
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#include <linux/stringify.h>
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#include <linux/types.h>
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#ifdef __KERNEL__
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#include <asm/processor.h>
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#include <asm/cmpxchg.h>
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#include <asm/barrier.h>
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#define ATOMIC_INIT(i) { (i) }
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/*
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* This Xtensa implementation assumes that the right mechanism
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* for exclusion is for locking interrupts to level EXCM_LEVEL.
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*
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* Locking interrupts looks like this:
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*
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* rsil a15, TOPLEVEL
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* <code>
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* wsr a15, PS
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* rsync
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*
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* Note that a15 is used here because the register allocation
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* done by the compiler is not guaranteed and a window overflow
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* may not occur between the rsil and wsr instructions. By using
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* a15 in the rsil, the machine is guaranteed to be in a state
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* where no register reference will cause an overflow.
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*/
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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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#define atomic_read(v) READ_ONCE((v)->counter)
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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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#if XCHAL_HAVE_S32C1I
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#define ATOMIC_OP(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 tmp; \
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int result; \
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\
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__asm__ __volatile__( \
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"1: l32i %1, %3, 0\n" \
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" wsr %1, scompare1\n" \
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" " #op " %0, %1, %2\n" \
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" s32c1i %0, %3, 0\n" \
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" bne %0, %1, 1b\n" \
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: "=&a" (result), "=&a" (tmp) \
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: "a" (i), "a" (v) \
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: "memory" \
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); \
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} \
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#define ATOMIC_OP_RETURN(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 tmp; \
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int result; \
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\
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__asm__ __volatile__( \
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"1: l32i %1, %3, 0\n" \
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" wsr %1, scompare1\n" \
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" " #op " %0, %1, %2\n" \
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" s32c1i %0, %3, 0\n" \
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" bne %0, %1, 1b\n" \
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" " #op " %0, %0, %2\n" \
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: "=&a" (result), "=&a" (tmp) \
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: "a" (i), "a" (v) \
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: "memory" \
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); \
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\
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return result; \
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}
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#else /* XCHAL_HAVE_S32C1I */
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#define ATOMIC_OP(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 vval; \
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\
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__asm__ __volatile__( \
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" rsil a15, "__stringify(TOPLEVEL)"\n"\
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" l32i %0, %2, 0\n" \
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" " #op " %0, %0, %1\n" \
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" s32i %0, %2, 0\n" \
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" wsr a15, ps\n" \
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" rsync\n" \
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: "=&a" (vval) \
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: "a" (i), "a" (v) \
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: "a15", "memory" \
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); \
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} \
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#define ATOMIC_OP_RETURN(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 vval; \
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\
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__asm__ __volatile__( \
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" rsil a15,"__stringify(TOPLEVEL)"\n" \
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" l32i %0, %2, 0\n" \
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" " #op " %0, %0, %1\n" \
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" s32i %0, %2, 0\n" \
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" wsr a15, ps\n" \
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" rsync\n" \
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: "=&a" (vval) \
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: "a" (i), "a" (v) \
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: "a15", "memory" \
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); \
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\
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return vval; \
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}
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#endif /* XCHAL_HAVE_S32C1I */
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#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
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ATOMIC_OPS(add)
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ATOMIC_OPS(sub)
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ATOMIC_OP(and)
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ATOMIC_OP(or)
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ATOMIC_OP(xor)
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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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/**
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* atomic_sub_and_test - subtract value from variable and test result
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* @i: integer value to subtract
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* @v: pointer of type atomic_t
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*
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* Atomically subtracts @i from @v and returns
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* true if the result is zero, or false for all
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* other cases.
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*/
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#define atomic_sub_and_test(i,v) (atomic_sub_return((i),(v)) == 0)
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/**
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* atomic_inc - increment atomic variable
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* @v: pointer of type atomic_t
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*
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* Atomically increments @v by 1.
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*/
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#define atomic_inc(v) atomic_add(1,(v))
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/**
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* atomic_inc - increment atomic variable
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* @v: pointer of type atomic_t
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*
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* Atomically increments @v by 1.
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*/
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#define atomic_inc_return(v) atomic_add_return(1,(v))
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/**
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* atomic_dec - decrement atomic variable
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* @v: pointer of type atomic_t
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*
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* Atomically decrements @v by 1.
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*/
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#define atomic_dec(v) atomic_sub(1,(v))
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/**
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* atomic_dec_return - decrement atomic variable
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* @v: pointer of type atomic_t
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*
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* Atomically decrements @v by 1.
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*/
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#define atomic_dec_return(v) atomic_sub_return(1,(v))
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/**
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* atomic_dec_and_test - decrement and test
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* @v: pointer of type atomic_t
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*
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* Atomically decrements @v by 1 and
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* returns true if the result is 0, or false for all other
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* cases.
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*/
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#define atomic_dec_and_test(v) (atomic_sub_return(1,(v)) == 0)
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/**
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* atomic_inc_and_test - increment and test
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* @v: pointer of type atomic_t
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*
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* Atomically increments @v by 1
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* and returns true if the result is zero, or false for all
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* other cases.
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*/
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#define atomic_inc_and_test(v) (atomic_add_return(1,(v)) == 0)
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/**
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* atomic_add_negative - add and test if negative
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* @v: pointer of type atomic_t
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* @i: integer value to add
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*
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* Atomically adds @i to @v and returns true
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* if the result is negative, or false when
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* result is greater than or equal to zero.
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*/
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#define atomic_add_negative(i,v) (atomic_add_return((i),(v)) < 0)
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#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
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#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
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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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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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for (;;) {
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if (unlikely(c == (u)))
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break;
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old = atomic_cmpxchg((v), c, c + (a));
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if (likely(old == c))
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break;
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c = old;
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}
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return c;
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}
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#endif /* __KERNEL__ */
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#endif /* _XTENSA_ATOMIC_H */
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