arch/sparc/include/asm/spinlock_32.h

Source file repositories/reference/linux-study-clean/arch/sparc/include/asm/spinlock_32.h

File Facts

System
Linux kernel
Corpus path
arch/sparc/include/asm/spinlock_32.h
Extension
.h
Size
4326 bytes
Lines
189
Domain
Architecture Layer
Bucket
arch/sparc
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 __SPARC_SPINLOCK_H
#define __SPARC_SPINLOCK_H

#ifndef __ASSEMBLER__

#include <asm/psr.h>
#include <asm/barrier.h>
#include <asm/processor.h> /* for cpu_relax */

#define arch_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0)

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
	__asm__ __volatile__(
	"\n1:\n\t"
	"ldstub	[%0], %%g2\n\t"
	"orcc	%%g2, 0x0, %%g0\n\t"
	"bne,a	2f\n\t"
	" ldub	[%0], %%g2\n\t"
	".subsection	2\n"
	"2:\n\t"
	"orcc	%%g2, 0x0, %%g0\n\t"
	"bne,a	2b\n\t"
	" ldub	[%0], %%g2\n\t"
	"b,a	1b\n\t"
	".previous\n"
	: /* no outputs */
	: "r" (lock)
	: "g2", "memory", "cc");
}

static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
	unsigned int result;
	__asm__ __volatile__("ldstub [%1], %0"
			     : "=r" (result)
			     : "r" (lock)
			     : "memory");
	return (result == 0);
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
	__asm__ __volatile__("stb %%g0, [%0]" : : "r" (lock) : "memory");
}

/* Read-write spinlocks, allowing multiple readers
 * but only one writer.
 *
 * NOTE! it is quite common to have readers in interrupts
 * but no interrupt writers. For those circumstances we
 * can "mix" irq-safe locks - any writer needs to get a
 * irq-safe write-lock, but readers can get non-irqsafe
 * read-locks.
 *
 * XXX This might create some problems with my dual spinlock
 * XXX scheme, deadlocks etc. -DaveM
 *
 * Sort of like atomic_t's on Sparc, but even more clever.
 *
 *	------------------------------------
 *	| 24-bit counter           | wlock |  arch_rwlock_t
 *	------------------------------------
 *	 31                       8 7     0
 *
 * wlock signifies the one writer is in or somebody is updating
 * counter. For a writer, if he successfully acquires the wlock,
 * but counter is non-zero, he has to release the lock and wait,
 * till both counter and wlock are zero.
 *
 * Unfortunately this scheme limits us to ~16,000,000 cpus.
 */
static inline void __arch_read_lock(arch_rwlock_t *rw)
{
	register arch_rwlock_t *lp asm("g1");
	lp = rw;
	__asm__ __volatile__(
	"mov	%%o7, %%g4\n\t"
	"call	___rw_read_enter\n\t"
	" ldstub	[%%g1 + 3], %%g2\n"
	: /* no outputs */
	: "r" (lp)
	: "g2", "g4", "memory", "cc");
}

#define arch_read_lock(lock) \
do {	unsigned long flags; \
	local_irq_save(flags); \
	__arch_read_lock(lock); \
	local_irq_restore(flags); \

Annotation

Implementation Notes