diff options
Diffstat (limited to 'arch/parisc/include/asm/spinlock.h')
| -rw-r--r-- | arch/parisc/include/asm/spinlock.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h new file mode 100644 index 000000000..8a63515f0 --- /dev/null +++ b/arch/parisc/include/asm/spinlock.h @@ -0,0 +1,169 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_SPINLOCK_H +#define __ASM_SPINLOCK_H + +#include <asm/barrier.h> +#include <asm/ldcw.h> +#include <asm/processor.h> +#include <asm/spinlock_types.h> + +static inline int arch_spin_is_locked(arch_spinlock_t *x) +{ + volatile unsigned int *a = __ldcw_align(x); + return *a == 0; +} + +#define arch_spin_lock(lock) arch_spin_lock_flags(lock, 0) + +static inline void arch_spin_lock_flags(arch_spinlock_t *x, + unsigned long flags) +{ + volatile unsigned int *a; + + a = __ldcw_align(x); + while (__ldcw(a) == 0) + while (*a == 0) + if (flags & PSW_SM_I) { + local_irq_enable(); + cpu_relax(); + local_irq_disable(); + } else + cpu_relax(); +} +#define arch_spin_lock_flags arch_spin_lock_flags + +static inline void arch_spin_unlock(arch_spinlock_t *x) +{ + volatile unsigned int *a; + + a = __ldcw_align(x); + mb(); + *a = 1; +} + +static inline int arch_spin_trylock(arch_spinlock_t *x) +{ + volatile unsigned int *a; + int ret; + + a = __ldcw_align(x); + ret = __ldcw(a) != 0; + + return ret; +} + +/* + * 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. + */ + +/* 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 arch_read_lock(arch_rwlock_t *rw) +{ + unsigned long flags; + local_irq_save(flags); + arch_spin_lock_flags(&rw->lock, flags); + rw->counter++; + arch_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__ void arch_read_unlock(arch_rwlock_t *rw) +{ + unsigned long flags; + local_irq_save(flags); + arch_spin_lock_flags(&rw->lock, flags); + rw->counter--; + arch_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 arch_read_trylock(arch_rwlock_t *rw) +{ + unsigned long flags; + retry: + local_irq_save(flags); + if (arch_spin_trylock(&rw->lock)) { + rw->counter++; + arch_spin_unlock(&rw->lock); + local_irq_restore(flags); + return 1; + } + + 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 (arch_spin_is_locked(&rw->lock) && rw->counter >= 0) + cpu_relax(); + + goto retry; +} + +/* 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 arch_write_lock(arch_rwlock_t *rw) +{ + unsigned long flags; +retry: + local_irq_save(flags); + arch_spin_lock_flags(&rw->lock, flags); + + if (rw->counter != 0) { + arch_spin_unlock(&rw->lock); + local_irq_restore(flags); + + while (rw->counter != 0) + cpu_relax(); + + goto retry; + } + + rw->counter = -1; /* mark as write-locked */ + mb(); + local_irq_restore(flags); +} + +static __inline__ void arch_write_unlock(arch_rwlock_t *rw) +{ + rw->counter = 0; + arch_spin_unlock(&rw->lock); +} + +/* 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 arch_write_trylock(arch_rwlock_t *rw) +{ + unsigned long flags; + int result = 0; + + local_irq_save(flags); + if (arch_spin_trylock(&rw->lock)) { + if (rw->counter == 0) { + rw->counter = -1; + result = 1; + } else { + /* Read-locked. Oh well. */ + arch_spin_unlock(&rw->lock); + } + } + local_irq_restore(flags); + + return result; +} + +#endif /* __ASM_SPINLOCK_H */ |