arch/openrisc/include/asm/cmpxchg.h

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

File Facts

System
Linux kernel
Corpus path
arch/openrisc/include/asm/cmpxchg.h
Extension
.h
Size
4059 bytes
Lines
172
Domain
Architecture Layer
Bucket
arch/openrisc
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_OPENRISC_CMPXCHG_H
#define __ASM_OPENRISC_CMPXCHG_H

#include  <linux/bits.h>
#include  <linux/compiler.h>
#include  <linux/types.h>

#define __HAVE_ARCH_CMPXCHG 1

static inline unsigned long cmpxchg_u32(volatile void *ptr,
		unsigned long old, unsigned long new)
{
	__asm__ __volatile__(
		"1:	l.lwa %0, 0(%1)		\n"
		"	l.sfeq %0, %2		\n"
		"	l.bnf 2f		\n"
		"	 l.nop			\n"
		"	l.swa 0(%1), %3		\n"
		"	l.bnf 1b		\n"
		"	 l.nop			\n"
		"2:				\n"
		: "=&r"(old)
		: "r"(ptr), "r"(old), "r"(new)
		: "cc", "memory");

	return old;
}

static inline unsigned long xchg_u32(volatile void *ptr,
		unsigned long val)
{
	__asm__ __volatile__(
		"1:	l.lwa %0, 0(%1)		\n"
		"	l.swa 0(%1), %2		\n"
		"	l.bnf 1b		\n"
		"	 l.nop			\n"
		: "=&r"(val)
		: "r"(ptr), "r"(val)
		: "cc", "memory");

	return val;
}

static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
				int size)
{
	int off = (unsigned long)ptr % sizeof(u32);
	volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
	int bitoff = off * BITS_PER_BYTE;
#endif
	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
	u32 load32, old32, new32;
	u32 ret;

	load32 = READ_ONCE(*p);

	while (true) {
		ret = (load32 & bitmask) >> bitoff;
		if (old != ret)
			return ret;

		old32 = (load32 & ~bitmask) | (old << bitoff);
		new32 = (load32 & ~bitmask) | (new << bitoff);

		/* Do 32 bit cmpxchg */
		load32 = cmpxchg_u32(p, old32, new32);
		if (load32 == old32)
			return old;
	}
}

/* xchg */

static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
{
	int off = (unsigned long)ptr % sizeof(u32);
	volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
	int bitoff = off * BITS_PER_BYTE;
#endif
	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
	u32 oldv, newv;
	u32 ret;

	do {

Annotation

Implementation Notes