arch/hexagon/include/asm/spinlock.h

Source file repositories/reference/linux-study-clean/arch/hexagon/include/asm/spinlock.h

File Facts

System
Linux kernel
Corpus path
arch/hexagon/include/asm/spinlock.h
Extension
.h
Size
3295 bytes
Lines
159
Domain
Architecture Layer
Bucket
arch/hexagon
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_SPINLOCK_H
#define _ASM_SPINLOCK_H

#include <asm/irqflags.h>
#include <asm/barrier.h>
#include <asm/processor.h>

/*
 * This file is pulled in for SMP builds.
 * Really need to check all the barrier stuff for "true" SMP
 */

/*
 * Read locks:
 * - load the lock value
 * - increment it
 * - if the lock value is still negative, go back and try again.
 * - unsuccessful store is unsuccessful.  Go back and try again.  Loser.
 * - successful store new lock value if positive -> lock acquired
 */
static inline void arch_read_lock(arch_rwlock_t *lock)
{
	__asm__ __volatile__(
		"1:	R6 = memw_locked(%0);\n"
		"	{ P3 = cmp.ge(R6,#0); R6 = add(R6,#1);}\n"
		"	{ if (!P3) jump 1b; }\n"
		"	memw_locked(%0,P3) = R6;\n"
		"	{ if (!P3) jump 1b; }\n"
		:
		: "r" (&lock->lock)
		: "memory", "r6", "p3"
	);

}

static inline void arch_read_unlock(arch_rwlock_t *lock)
{
	__asm__ __volatile__(
		"1:	R6 = memw_locked(%0);\n"
		"	R6 = add(R6,#-1);\n"
		"	memw_locked(%0,P3) = R6\n"
		"	if (!P3) jump 1b;\n"
		:
		: "r" (&lock->lock)
		: "memory", "r6", "p3"
	);

}

/*  I think this returns 0 on fail, 1 on success.  */
static inline int arch_read_trylock(arch_rwlock_t *lock)
{
	int temp;
	__asm__ __volatile__(
		"	R6 = memw_locked(%1);\n"
		"	{ %0 = #0; P3 = cmp.ge(R6,#0); R6 = add(R6,#1);}\n"
		"	{ if (!P3) jump 1f; }\n"
		"	memw_locked(%1,P3) = R6;\n"
		"	{ %0 = P3 }\n"
		"1:\n"
		: "=&r" (temp)
		: "r" (&lock->lock)
		: "memory", "r6", "p3"
	);
	return temp;
}

/*  Stuffs a -1 in the lock value?  */
static inline void arch_write_lock(arch_rwlock_t *lock)
{
	__asm__ __volatile__(
		"1:	R6 = memw_locked(%0)\n"
		"	{ P3 = cmp.eq(R6,#0);  R6 = #-1;}\n"
		"	{ if (!P3) jump 1b; }\n"
		"	memw_locked(%0,P3) = R6;\n"
		"	{ if (!P3) jump 1b; }\n"
		:
		: "r" (&lock->lock)
		: "memory", "r6", "p3"
	);
}


static inline int arch_write_trylock(arch_rwlock_t *lock)
{
	int temp;
	__asm__ __volatile__(
		"	R6 = memw_locked(%1)\n"
		"	{ %0 = #0; P3 = cmp.eq(R6,#0);  R6 = #-1;}\n"
		"	{ if (!P3) jump 1f; }\n"

Annotation

Implementation Notes