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/* spinlock.h: 32-bit Sparc spinlock support.
*
* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
*/
#ifndef __SPARC_SPINLOCK_H
#define __SPARC_SPINLOCK_H
#include <linux/threads.h> /* For NR_CPUS */
#ifndef __ASSEMBLY__
#include <asm/psr.h>
#define __raw_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0)
#define __raw_spin_unlock_wait(lock) \
do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
static inline void __raw_spin_lock(raw_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 __raw_spin_trylock(raw_spinlock_t *lock)
{
unsigned int result;
__asm__ __volatile__("ldstub [%1], %0"
: "=r" (result)
: "r" (lock)
: "memory");
return (result == 0);
}
static inline void __raw_spin_unlock(raw_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 | raw_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 __read_lock(raw_rwlock_t *rw)
{
register raw_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 __raw_read_lock(lock) \
do { unsigned long flags; \
local_irq_save(flags); \
__read_lock(lock); \
local_irq_restore(flags); \
} while(0)
static inline void __read_unlock(raw_rwlock_t *rw)
{
register raw_rwlock_t *lp asm("g1");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_read_exit\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: /* no outputs */
: "r" (lp)
: "g2", "g4", "memory", "cc");
}
#define __raw_read_unlock(lock) \
do { unsigned long flags; \
local_irq_save(flags); \
__read_unlock(lock); \
local_irq_restore(flags); \
} while(0)
static inline void __raw_write_lock(raw_rwlock_t *rw)
{
register raw_rwlock_t *lp asm("g1");
lp = rw;
__asm__ __volatile__(
"mov %%o7, %%g4\n\t"
"call ___rw_write_enter\n\t"
" ldstub [%%g1 + 3], %%g2\n"
: /* no outputs */
: "r" (lp)
: "g2", "g4", "memory", "cc");
}
static inline int __raw_write_trylock(raw_rwlock_t *rw)
{
unsigned int val;
__asm__ __volatile__("ldstub [%1 + 3], %0"
: "=r" (val)
: "r" (&rw->lock)
: "memory");
if (val == 0) {
val = rw->lock & ~0xff;
if (val)
((volatile u8*)&rw->lock)[3] = 0;
}
return (val == 0);
}
#define __raw_write_unlock(rw) do { (rw)->lock = 0; } while(0)
#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
#define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
#define __raw_read_can_lock(rw) (!((rw)->lock & 0xff))
#define __raw_write_can_lock(rw) (!(rw)->lock)
#endif /* !(__ASSEMBLY__) */
#endif /* __SPARC_SPINLOCK_H */
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