/* 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 */
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assembly.h | File | 12.94 KB | 0644 |
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irq.h | File | 1.23 KB | 0644 |
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irqflags.h | File | 1.02 KB | 0644 |
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ldcw.h | File | 2.15 KB | 0644 |
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processor.h | File | 9.86 KB | 0644 |
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ropes.h | File | 9.73 KB | 0644 |
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runway.h | File | 320 B | 0644 |
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smp.h | File | 1.25 KB | 0644 |
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special_insns.h | File | 1015 B | 0644 |
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spinlock.h | File | 4.02 KB | 0644 |
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spinlock_types.h | File | 483 B | 0644 |
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