arch/arc/include/asm/cmpxchg.h

Source file repositories/reference/linux-study-clean/arch/arc/include/asm/cmpxchg.h

File Facts

System
Linux kernel
Corpus path
arch/arc/include/asm/cmpxchg.h
Extension
.h
Size
3321 bytes
Lines
146
Domain
Architecture Layer
Bucket
arch/arc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef __ASM_ARC_CMPXCHG_H
#define __ASM_ARC_CMPXCHG_H

#include <linux/build_bug.h>
#include <linux/types.h>
#include <linux/cmpxchg-emu.h>

#include <asm/barrier.h>
#include <asm/smp.h>

#ifdef CONFIG_ARC_HAS_LLSC

/*
 * if (*ptr == @old)
 *      *ptr = @new
 */
#define __cmpxchg(ptr, old, new)					\
({									\
	__typeof__(*(ptr)) _prev;					\
									\
	__asm__ __volatile__(						\
	"1:	llock  %0, [%1]	\n"					\
	"	brne   %0, %2, 2f	\n"				\
	"	scond  %3, [%1]	\n"					\
	"	bnz     1b		\n"				\
	"2:				\n"				\
	: "=&r"(_prev)	/* Early clobber prevent reg reuse */		\
	: "r"(ptr),	/* Not "m": llock only supports reg */		\
	  "ir"(old),							\
	  "r"(new)	/* Not "ir": scond can't take LIMM */		\
	: "cc",								\
	  "memory");	/* gcc knows memory is clobbered */		\
									\
	_prev;								\
})

#define arch_cmpxchg_relaxed(ptr, old, new)				\
({									\
	__typeof__(ptr) _p_ = (ptr);					\
	__typeof__(*(ptr)) _o_ = (old);					\
	__typeof__(*(ptr)) _n_ = (new);					\
	__typeof__(*(ptr)) _prev_;					\
									\
	switch(sizeof((_p_))) {						\
	case 1:								\
		_prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *__force)_p_, (uintptr_t)_o_, (uintptr_t)_n_);	\
		break;							\
	case 4:								\
		_prev_ = __cmpxchg(_p_, _o_, _n_);			\
		break;							\
	default:							\
		BUILD_BUG();						\
	}								\
	_prev_;								\
})

#else

#define arch_cmpxchg(ptr, old, new)				        \
({									\
	volatile __typeof__(ptr) _p_ = (ptr);				\
	__typeof__(*(ptr)) _o_ = (old);					\
	__typeof__(*(ptr)) _n_ = (new);					\
	__typeof__(*(ptr)) _prev_;					\
	unsigned long __flags;						\
									\
	/*								\
	 * spin lock/unlock provide the needed smp_mb() before/after	\
	 */								\
	atomic_ops_lock(__flags);					\
	_prev_ = *_p_;							\
	if (_prev_ == _o_)						\
		*_p_ = _n_;						\
	atomic_ops_unlock(__flags);					\
	_prev_;								\
})

#endif

/*
 * xchg
 */
#ifdef CONFIG_ARC_HAS_LLSC

#define __arch_xchg(ptr, val)						\
({									\
	__asm__ __volatile__(						\
	"	ex  %0, [%1]	\n"	/* set new value */	        \
	: "+r"(val)							\
	: "r"(ptr)							\

Annotation

Implementation Notes