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

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#ifndef __ASM_GENERIC_CMPXCHG_LOCAL_H

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#define __ASM_GENERIC_CMPXCHG_LOCAL_H

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#include <linux/types.h>

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#include <linux/irqflags.h>

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extern unsigned long wrong_size_cmpxchg(volatile void *ptr)

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	__noreturn;

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/*

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 * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned

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 * long parameter, supporting various types of architectures.

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 */

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static inline unsigned long __generic_cmpxchg_local(volatile void *ptr,

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		unsigned long old, unsigned long new, int size)

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{

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	unsigned long flags, prev;

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	/*

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	 * Sanity checking, compile-time.

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	 */

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	if (size == 8 && sizeof(unsigned long) != 8)

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		wrong_size_cmpxchg(ptr);

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	raw_local_irq_save(flags);

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	switch (size) {

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	case 1: prev = *(u8 *)ptr;

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		if (prev == (old & 0xffu))

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			*(u8 *)ptr = (new & 0xffu);

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		break;

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	case 2: prev = *(u16 *)ptr;

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		if (prev == (old & 0xffffu))

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			*(u16 *)ptr = (new & 0xffffu);

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		break;

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	case 4: prev = *(u32 *)ptr;

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		if (prev == (old & 0xffffffffu))

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			*(u32 *)ptr = (new & 0xffffffffu);

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		break;

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	case 8: prev = *(u64 *)ptr;

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		if (prev == old)

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			*(u64 *)ptr = (u64)new;

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		break;

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	default:

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		wrong_size_cmpxchg(ptr);

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	}

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	raw_local_irq_restore(flags);

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	return prev;

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}

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/*

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 * Generic version of __cmpxchg64_local. Takes an u64 parameter.

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 */

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static inline u64 __generic_cmpxchg64_local(volatile void *ptr,

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		u64 old, u64 new)

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{

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	u64 prev;

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	unsigned long flags;

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	raw_local_irq_save(flags);

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	prev = *(u64 *)ptr;

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	if (prev == old)

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		*(u64 *)ptr = new;

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	raw_local_irq_restore(flags);

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	return prev;

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}

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#endif

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