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#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/atomic.h>
#include <asm/rwlock.h>
#include <asm/page.h>
extern int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2)));
/* It seems that people are forgetting to
* initialize their spinlocks properly, tsk tsk.
* Remember to turn this off in 2.4. -ben
*/
#define SPINLOCK_DEBUG 0
/*
* Your basic SMP spinlocks, allowing only a single CPU anywhere
*/
typedef struct {
volatile unsigned int lock;
#if SPINLOCK_DEBUG
unsigned magic;
#endif
} spinlock_t;
#define SPINLOCK_MAGIC 0xdead4ead
#if SPINLOCK_DEBUG
#define SPINLOCK_MAGIC_INIT , SPINLOCK_MAGIC
#else
#define SPINLOCK_MAGIC_INIT /* */
#endif
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 SPINLOCK_MAGIC_INIT }
#define spin_lock_init(x) do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
/*
* Simple spin lock operations. There are two variants, one clears IRQ's
* on the local processor, one does not.
*
* We make no fairness assumptions. They have a cost.
*/
#define spin_is_locked(x) (*(volatile char *)(&(x)->lock) <= 0)
#define spin_unlock_wait(x) do { barrier(); } while(spin_is_locked(x))
#define spin_lock_string \
"\n1:\t" \
"lock ; decb %0\n\t" \
"js 2f\n" \
".section .text.lock,\"ax\"\n" \
"2:\t" \
"cmpb $0,%0\n\t" \
"rep;nop\n\t" \
"jle 2b\n\t" \
"jmp 1b\n" \
".previous"
/*
* This works. Despite all the confusion.
*/
#define spin_unlock_string \
"movb $1,%0"
static inline int spin_trylock(spinlock_t *lock)
{
char oldval;
__asm__ __volatile__(
"xchgb %b0,%1"
:"=q" (oldval), "=m" (__dummy_lock(lock))
:"0" (0));
return oldval > 0;
}
extern inline void spin_lock(spinlock_t *lock)
{
#if SPINLOCK_DEBUG
__label__ here;
here:
if (lock->magic != SPINLOCK_MAGIC) {
printk("eip: %p\n", &&here);
BUG();
}
#endif
__asm__ __volatile__(
spin_lock_string
:"=m" (__dummy_lock(lock)));
}
extern inline void spin_unlock(spinlock_t *lock)
{
#if SPINLOCK_DEBUG
if (lock->magic != SPINLOCK_MAGIC)
BUG();
if (!spin_is_locked(lock))
BUG();
#endif
__asm__ __volatile__(
spin_unlock_string
:"=m" (__dummy_lock(lock)));
}
/*
* 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.
*/
typedef struct {
volatile unsigned int lock;
#if SPINLOCK_DEBUG
unsigned magic;
#endif
} rwlock_t;
#define RWLOCK_MAGIC 0xdeaf1eed
#if SPINLOCK_DEBUG
#define RWLOCK_MAGIC_INIT , RWLOCK_MAGIC
#else
#define RWLOCK_MAGIC_INIT /* */
#endif
#define RW_LOCK_UNLOCKED (rwlock_t) { RW_LOCK_BIAS RWLOCK_MAGIC_INIT }
#define rwlock_init(x) do { *(x) = RW_LOCK_UNLOCKED; } while(0)
/*
* On x86, we implement read-write locks as a 32-bit counter
* with the high bit (sign) being the "contended" bit.
*
* The inline assembly is non-obvious. Think about it.
*
* Changed to use the same technique as rw semaphores. See
* semaphore.h for details. -ben
*/
/* the spinlock helpers are in arch/i386/kernel/semaphore.S */
extern inline void read_lock(rwlock_t *rw)
{
#if SPINLOCK_DEBUG
if (rw->magic != RWLOCK_MAGIC)
BUG();
#endif
__build_read_lock(rw, "__read_lock_failed");
}
extern inline void write_lock(rwlock_t *rw)
{
#if SPINLOCK_DEBUG
if (rw->magic != RWLOCK_MAGIC)
BUG();
#endif
__build_write_lock(rw, "__write_lock_failed");
}
#define read_unlock(rw) asm volatile("lock ; incl %0" :"=m" (__dummy_lock(&(rw)->lock)))
#define write_unlock(rw) asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0":"=m" (__dummy_lock(&(rw)->lock)))
extern inline int write_trylock(rwlock_t *lock)
{
atomic_t *count = (atomic_t *)lock;
if (atomic_sub_and_test(RW_LOCK_BIAS, count))
return 1;
atomic_add(RW_LOCK_BIAS, count);
return 0;
}
#endif /* __ASM_SPINLOCK_H */
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