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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/include/asm-generic/cmpxchg.h
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/* SPDX-License-Identifier: GPL-2.0 */

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/*

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 * Generic UP xchg and cmpxchg using interrupt disablement.  Does not

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 * support SMP.

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 */

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#ifndef __ASM_GENERIC_CMPXCHG_H

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#define __ASM_GENERIC_CMPXCHG_H

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#ifdef CONFIG_SMP

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#error "Cannot use generic cmpxchg on SMP"

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#endif

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#include <linux/types.h>

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#include <linux/irqflags.h>

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/*

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 * This function doesn't exist, so you'll get a linker error if

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 * something tries to do an invalidly-sized xchg().

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 */

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extern void __generic_xchg_called_with_bad_pointer(void);

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static inline

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unsigned long __generic_xchg(unsigned long x, volatile void *ptr, int size)

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{

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	unsigned long ret, flags;

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	switch (size) {

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	case 1:

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#ifdef __xchg_u8

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		return __xchg_u8(x, ptr);

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#else

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		local_irq_save(flags);

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		ret = *(volatile u8 *)ptr;

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		*(volatile u8 *)ptr = (x & 0xffu);

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		local_irq_restore(flags);

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		return ret;

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#endif /* __xchg_u8 */

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	case 2:

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#ifdef __xchg_u16

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		return __xchg_u16(x, ptr);

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#else

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		local_irq_save(flags);

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		ret = *(volatile u16 *)ptr;

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		*(volatile u16 *)ptr = (x & 0xffffu);

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		local_irq_restore(flags);

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		return ret;

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#endif /* __xchg_u16 */

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	case 4:

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#ifdef __xchg_u32

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		return __xchg_u32(x, ptr);

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#else

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		local_irq_save(flags);

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		ret = *(volatile u32 *)ptr;

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		*(volatile u32 *)ptr = (x & 0xffffffffu);

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		local_irq_restore(flags);

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		return ret;

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#endif /* __xchg_u32 */

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#ifdef CONFIG_64BIT

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	case 8:

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#ifdef __xchg_u64

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		return __xchg_u64(x, ptr);

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#else

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		local_irq_save(flags);

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		ret = *(volatile u64 *)ptr;

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		*(volatile u64 *)ptr = x;

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		local_irq_restore(flags);

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		return ret;

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#endif /* __xchg_u64 */

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#endif /* CONFIG_64BIT */

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	default:

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		__generic_xchg_called_with_bad_pointer();

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		return x;

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	}

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}

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#define generic_xchg(ptr, x) ({							\

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	((__typeof__(*(ptr)))							\

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		__generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));	\

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})

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/*

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 * Atomic compare and exchange.

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 */

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#include <asm-generic/cmpxchg-local.h>

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#define generic_cmpxchg_local(ptr, o, n) ({					\

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	((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o),	\

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			(unsigned long)(n), sizeof(*(ptr))));			\

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})

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#define generic_cmpxchg64_local(ptr, o, n) \

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	__generic_cmpxchg64_local((ptr), (o), (n))

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#ifndef arch_xchg

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#define arch_xchg		generic_xchg

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#endif

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#ifndef arch_cmpxchg_local

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#define arch_cmpxchg_local	generic_cmpxchg_local

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#endif

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#ifndef arch_cmpxchg64_local

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#define arch_cmpxchg64_local	generic_cmpxchg64_local

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#endif

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#define arch_cmpxchg		arch_cmpxchg_local

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#define arch_cmpxchg64		arch_cmpxchg64_local

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#endif /* __ASM_GENERIC_CMPXCHG_H */

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