X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=include%2Fasm-parisc%2Fspinlock.h;h=f3d2090a18dc316e5a4cbd388abb32e94717b764;hb=97bf2856c6014879bd04983a3e9dfcdac1e7fe85;hp=7a2c25d477b5b9a85da41cb82a9a90fb8385a268;hpb=9bf4aaab3e101692164d49b7ca357651eb691cb6;p=linux-2.6.git diff --git a/include/asm-parisc/spinlock.h b/include/asm-parisc/spinlock.h index 7a2c25d47..f3d2090a1 100644 --- a/include/asm-parisc/spinlock.h +++ b/include/asm-parisc/spinlock.h @@ -2,220 +2,193 @@ #define __ASM_SPINLOCK_H #include +#include +#include -/* Note that PA-RISC has to use `1' to mean unlocked and `0' to mean locked - * since it only has load-and-zero. Moreover, at least on some PA processors, - * the semaphore address has to be 16-byte aligned. - */ - -#ifndef CONFIG_DEBUG_SPINLOCK - -#define __SPIN_LOCK_UNLOCKED { { 1, 1, 1, 1 } } -#undef SPIN_LOCK_UNLOCKED -#define SPIN_LOCK_UNLOCKED (spinlock_t) __SPIN_LOCK_UNLOCKED - -#define spin_lock_init(x) do { *(x) = SPIN_LOCK_UNLOCKED; } while(0) - -static inline int spin_is_locked(spinlock_t *x) +static inline int __raw_spin_is_locked(raw_spinlock_t *x) { volatile unsigned int *a = __ldcw_align(x); return *a == 0; } -#define spin_unlock_wait(x) do { barrier(); } while(spin_is_locked(x)) -#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock) +#define __raw_spin_lock(lock) __raw_spin_lock_flags(lock, 0) +#define __raw_spin_unlock_wait(x) \ + do { cpu_relax(); } while (__raw_spin_is_locked(x)) -static inline void _raw_spin_lock(spinlock_t *x) +static inline void __raw_spin_lock_flags(raw_spinlock_t *x, + unsigned long flags) { - volatile unsigned int *a = __ldcw_align(x); + volatile unsigned int *a; + + mb(); + a = __ldcw_align(x); while (__ldcw(a) == 0) - while (*a == 0); + while (*a == 0) + if (flags & PSW_SM_I) { + local_irq_enable(); + cpu_relax(); + local_irq_disable(); + } else + cpu_relax(); + mb(); } -static inline void _raw_spin_unlock(spinlock_t *x) +static inline void __raw_spin_unlock(raw_spinlock_t *x) { - volatile unsigned int *a = __ldcw_align(x); + volatile unsigned int *a; + mb(); + a = __ldcw_align(x); *a = 1; + mb(); } -static inline int _raw_spin_trylock(spinlock_t *x) +static inline int __raw_spin_trylock(raw_spinlock_t *x) { - volatile unsigned int *a = __ldcw_align(x); - return __ldcw(a) != 0; + volatile unsigned int *a; + int ret; + + mb(); + a = __ldcw_align(x); + ret = __ldcw(a) != 0; + mb(); + + return ret; } - -#define spin_lock_own(LOCK, LOCATION) ((void)0) - -#else /* !(CONFIG_DEBUG_SPINLOCK) */ - -#define SPINLOCK_MAGIC 0x1D244B3C - -#define __SPIN_LOCK_UNLOCKED { { 1, 1, 1, 1 }, SPINLOCK_MAGIC, 10, __FILE__ , NULL, 0, -1, NULL, NULL } -#undef SPIN_LOCK_UNLOCKED -#define SPIN_LOCK_UNLOCKED (spinlock_t) __SPIN_LOCK_UNLOCKED - -#define spin_lock_init(x) do { *(x) = SPIN_LOCK_UNLOCKED; } while(0) - -#define CHECK_LOCK(x) \ - do { \ - if (unlikely((x)->magic != SPINLOCK_MAGIC)) { \ - printk(KERN_ERR "%s:%d: spin_is_locked" \ - " on uninitialized spinlock %p.\n", \ - __FILE__, __LINE__, (x)); \ - } \ - } while(0) - -#define spin_is_locked(x) \ - ({ \ - CHECK_LOCK(x); \ - volatile unsigned int *a = __ldcw_align(x); \ - if (unlikely((*a == 0) && (x)->babble)) { \ - (x)->babble--; \ - printk("KERN_WARNING \ - %s:%d: spin_is_locked(%s/%p) already" \ - " locked by %s:%d in %s at %p(%d)\n", \ - __FILE__,__LINE__, (x)->module, (x), \ - (x)->bfile, (x)->bline, (x)->task->comm,\ - (x)->previous, (x)->oncpu); \ - } \ - *a == 0; \ - }) - -#define spin_unlock_wait(x) \ - do { \ - CHECK_LOCK(x); \ - volatile unsigned int *a = __ldcw_align(x); \ - if (unlikely((*a == 0) && (x)->babble)) { \ - (x)->babble--; \ - printk("KERN_WARNING \ - %s:%d: spin_unlock_wait(%s/%p)" \ - " owned by %s:%d in %s at %p(%d)\n", \ - __FILE__,__LINE__, (x)->module, (x), \ - (x)->bfile, (x)->bline, (x)->task->comm,\ - (x)->previous, (x)->oncpu); \ - } \ - barrier(); \ - } while (*((volatile unsigned char *)(__ldcw_align(x))) == 0) - -extern void _dbg_spin_lock(spinlock_t *lock, const char *base_file, int line_no); -extern void _dbg_spin_unlock(spinlock_t *lock, const char *, int); -extern int _dbg_spin_trylock(spinlock_t * lock, const char *, int); - -#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock) - -#define _raw_spin_unlock(lock) _dbg_spin_unlock(lock, __FILE__, __LINE__) -#define _raw_spin_lock(lock) _dbg_spin_lock(lock, __FILE__, __LINE__) -#define _raw_spin_trylock(lock) _dbg_spin_trylock(lock, __FILE__, __LINE__) - -/* just in case we need it */ -#define spin_lock_own(LOCK, LOCATION) \ -do { \ - volatile unsigned int *a = __ldcw_align(LOCK); \ - if (!((*a == 0) && ((LOCK)->oncpu == smp_processor_id()))) \ - printk("KERN_WARNING \ - %s: called on %d from %p but lock %s on %d\n", \ - LOCATION, smp_processor_id(), \ - __builtin_return_address(0), \ - (*a == 0) ? "taken" : "freed", (LOCK)->on_cpu); \ -} while (0) - -#endif /* !(CONFIG_DEBUG_SPINLOCK) */ /* - * Read-write spinlocks, allowing multiple readers - * but only one writer. + * Read-write spinlocks, allowing multiple readers but only one writer. + * Linux rwlocks are unfair to writers; they can be starved for an indefinite + * time by readers. With care, they can also be taken in interrupt context. + * + * In the PA-RISC implementation, we have a spinlock and a counter. + * Readers use the lock to serialise their access to the counter (which + * records how many readers currently hold the lock). + * Writers hold the spinlock, preventing any readers or other writers from + * grabbing the rwlock. */ -typedef struct { - spinlock_t lock; - volatile int counter; -} rwlock_t; -#define RW_LOCK_UNLOCKED (rwlock_t) { __SPIN_LOCK_UNLOCKED, 0 } - -#define rwlock_init(lp) do { *(lp) = RW_LOCK_UNLOCKED; } while (0) - -#define rwlock_is_locked(lp) ((lp)->counter != 0) - -/* read_lock, read_unlock are pretty straightforward. Of course it somehow - * sucks we end up saving/restoring flags twice for read_lock_irqsave aso. */ - -#ifdef CONFIG_DEBUG_RWLOCK -extern void _dbg_read_lock(rwlock_t * rw, const char *bfile, int bline); -#define _raw_read_lock(rw) _dbg_read_lock(rw, __FILE__, __LINE__) -#else -static __inline__ void _raw_read_lock(rwlock_t *rw) +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock */ +static __inline__ void __raw_read_lock(raw_rwlock_t *rw) { unsigned long flags; local_irq_save(flags); - _raw_spin_lock(&rw->lock); - + __raw_spin_lock_flags(&rw->lock, flags); rw->counter++; - - _raw_spin_unlock(&rw->lock); + __raw_spin_unlock(&rw->lock); local_irq_restore(flags); } -#endif /* CONFIG_DEBUG_RWLOCK */ -static __inline__ void _raw_read_unlock(rwlock_t *rw) +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock */ +static __inline__ void __raw_read_unlock(raw_rwlock_t *rw) { unsigned long flags; local_irq_save(flags); - _raw_spin_lock(&rw->lock); - + __raw_spin_lock_flags(&rw->lock, flags); rw->counter--; + __raw_spin_unlock(&rw->lock); + local_irq_restore(flags); +} + +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock */ +static __inline__ int __raw_read_trylock(raw_rwlock_t *rw) +{ + unsigned long flags; + retry: + local_irq_save(flags); + if (__raw_spin_trylock(&rw->lock)) { + rw->counter++; + __raw_spin_unlock(&rw->lock); + local_irq_restore(flags); + return 1; + } - _raw_spin_unlock(&rw->lock); local_irq_restore(flags); + /* If write-locked, we fail to acquire the lock */ + if (rw->counter < 0) + return 0; + + /* Wait until we have a realistic chance at the lock */ + while (__raw_spin_is_locked(&rw->lock) && rw->counter >= 0) + cpu_relax(); + + goto retry; } -/* write_lock is less trivial. We optimistically grab the lock and check - * if we surprised any readers. If so we release the lock and wait till - * they're all gone before trying again - * - * Also note that we don't use the _irqsave / _irqrestore suffixes here. - * If we're called with interrupts enabled and we've got readers (or other - * writers) in interrupt handlers someone fucked up and we'd dead-lock - * sooner or later anyway. prumpf */ - -#ifdef CONFIG_DEBUG_RWLOCK -extern void _dbg_write_lock(rwlock_t * rw, const char *bfile, int bline); -#define _raw_write_lock(rw) _dbg_write_lock(rw, __FILE__, __LINE__) -#else -static __inline__ void _raw_write_lock(rwlock_t *rw) +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to read_trylock() this lock */ +static __inline__ void __raw_write_lock(raw_rwlock_t *rw) { + unsigned long flags; retry: - _raw_spin_lock(&rw->lock); + local_irq_save(flags); + __raw_spin_lock_flags(&rw->lock, flags); - if(rw->counter != 0) { - /* this basically never happens */ - _raw_spin_unlock(&rw->lock); + if (rw->counter != 0) { + __raw_spin_unlock(&rw->lock); + local_irq_restore(flags); - while(rw->counter != 0); + while (rw->counter != 0) + cpu_relax(); goto retry; } - /* got it. now leave without unlocking */ - rw->counter = -1; /* remember we are locked */ + rw->counter = -1; /* mark as write-locked */ + mb(); + local_irq_restore(flags); } -#endif /* CONFIG_DEBUG_RWLOCK */ - -/* write_unlock is absolutely trivial - we don't have to wait for anything */ -static __inline__ void _raw_write_unlock(rwlock_t *rw) +static __inline__ void __raw_write_unlock(raw_rwlock_t *rw) { rw->counter = 0; - _raw_spin_unlock(&rw->lock); + __raw_spin_unlock(&rw->lock); } -static __inline__ int is_read_locked(rwlock_t *rw) +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to read_trylock() this lock */ +static __inline__ int __raw_write_trylock(raw_rwlock_t *rw) { - return rw->counter > 0; + unsigned long flags; + int result = 0; + + local_irq_save(flags); + if (__raw_spin_trylock(&rw->lock)) { + if (rw->counter == 0) { + rw->counter = -1; + result = 1; + } else { + /* Read-locked. Oh well. */ + __raw_spin_unlock(&rw->lock); + } + } + local_irq_restore(flags); + + return result; } -static __inline__ int is_write_locked(rwlock_t *rw) +/* + * read_can_lock - would read_trylock() succeed? + * @lock: the rwlock in question. + */ +static __inline__ int __raw_read_can_lock(raw_rwlock_t *rw) { - return rw->counter < 0; + return rw->counter >= 0; } +/* + * write_can_lock - would write_trylock() succeed? + * @lock: the rwlock in question. + */ +static __inline__ int __raw_write_can_lock(raw_rwlock_t *rw) +{ + return !rw->counter; +} + +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + #endif /* __ASM_SPINLOCK_H */