| | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| | 2 | #ifndef __ASM_SPINLOCK_H |
| | 3 | #define __ASM_SPINLOCK_H |
| | 4 | |
| | 5 | #include <asm/barrier.h> |
| | 6 | #include <asm/ldcw.h> |
| | 7 | #include <asm/processor.h> |
| | 8 | #include <asm/spinlock_types.h> |
| | 9 | |
| | 10 | static inline int arch_spin_is_locked(arch_spinlock_t *x) |
| | 11 | { |
| | 12 | volatile unsigned int *a = __ldcw_align(x); |
| | 13 | return *a == 0; |
| | 14 | } |
| | 15 | |
| | 16 | #define arch_spin_lock(lock) arch_spin_lock_flags(lock, 0) |
| | 17 | |
| | 18 | static inline void arch_spin_lock_flags(arch_spinlock_t *x, |
| | 19 | unsigned long flags) |
| | 20 | { |
| | 21 | volatile unsigned int *a; |
| | 22 | |
| | 23 | a = __ldcw_align(x); |
| | 24 | while (__ldcw(a) == 0) |
| | 25 | while (*a == 0) |
| | 26 | if (flags & PSW_SM_I) { |
| | 27 | local_irq_enable(); |
| | 28 | cpu_relax(); |
| | 29 | local_irq_disable(); |
| | 30 | } else |
| | 31 | cpu_relax(); |
| | 32 | } |
| | 33 | #define arch_spin_lock_flags arch_spin_lock_flags |
| | 34 | |
| | 35 | static inline void arch_spin_unlock(arch_spinlock_t *x) |
| | 36 | { |
| | 37 | volatile unsigned int *a; |
| | 38 | |
| | 39 | a = __ldcw_align(x); |
| | 40 | mb(); |
| | 41 | *a = 1; |
| | 42 | } |
| | 43 | |
| | 44 | static inline int arch_spin_trylock(arch_spinlock_t *x) |
| | 45 | { |
| | 46 | volatile unsigned int *a; |
| | 47 | int ret; |
| | 48 | |
| | 49 | a = __ldcw_align(x); |
| | 50 | ret = __ldcw(a) != 0; |
| | 51 | |
| | 52 | return ret; |
| | 53 | } |
| | 54 | |
| | 55 | /* |
| | 56 | * Read-write spinlocks, allowing multiple readers but only one writer. |
| | 57 | * Linux rwlocks are unfair to writers; they can be starved for an indefinite |
| | 58 | * time by readers. With care, they can also be taken in interrupt context. |
| | 59 | * |
| | 60 | * In the PA-RISC implementation, we have a spinlock and a counter. |
| | 61 | * Readers use the lock to serialise their access to the counter (which |
| | 62 | * records how many readers currently hold the lock). |
| | 63 | * Writers hold the spinlock, preventing any readers or other writers from |
| | 64 | * grabbing the rwlock. |
| | 65 | */ |
| | 66 | |
| | 67 | /* Note that we have to ensure interrupts are disabled in case we're |
| | 68 | * interrupted by some other code that wants to grab the same read lock */ |
| | 69 | static __inline__ void arch_read_lock(arch_rwlock_t *rw) |
| | 70 | { |
| | 71 | unsigned long flags; |
| | 72 | local_irq_save(flags); |
| | 73 | arch_spin_lock_flags(&rw->lock, flags); |
| | 74 | rw->counter++; |
| | 75 | arch_spin_unlock(&rw->lock); |
| | 76 | local_irq_restore(flags); |
| | 77 | } |
| | 78 | |
| | 79 | /* Note that we have to ensure interrupts are disabled in case we're |
| | 80 | * interrupted by some other code that wants to grab the same read lock */ |
| | 81 | static __inline__ void arch_read_unlock(arch_rwlock_t *rw) |
| | 82 | { |
| | 83 | unsigned long flags; |
| | 84 | local_irq_save(flags); |
| | 85 | arch_spin_lock_flags(&rw->lock, flags); |
| | 86 | rw->counter--; |
| | 87 | arch_spin_unlock(&rw->lock); |
| | 88 | local_irq_restore(flags); |
| | 89 | } |
| | 90 | |
| | 91 | /* Note that we have to ensure interrupts are disabled in case we're |
| | 92 | * interrupted by some other code that wants to grab the same read lock */ |
| | 93 | static __inline__ int arch_read_trylock(arch_rwlock_t *rw) |
| | 94 | { |
| | 95 | unsigned long flags; |
| | 96 | retry: |
| | 97 | local_irq_save(flags); |
| | 98 | if (arch_spin_trylock(&rw->lock)) { |
| | 99 | rw->counter++; |
| | 100 | arch_spin_unlock(&rw->lock); |
| | 101 | local_irq_restore(flags); |
| | 102 | return 1; |
| | 103 | } |
| | 104 | |
| | 105 | local_irq_restore(flags); |
| | 106 | /* If write-locked, we fail to acquire the lock */ |
| | 107 | if (rw->counter < 0) |
| | 108 | return 0; |
| | 109 | |
| | 110 | /* Wait until we have a realistic chance at the lock */ |
| | 111 | while (arch_spin_is_locked(&rw->lock) && rw->counter >= 0) |
| | 112 | cpu_relax(); |
| | 113 | |
| | 114 | goto retry; |
| | 115 | } |
| | 116 | |
| | 117 | /* Note that we have to ensure interrupts are disabled in case we're |
| | 118 | * interrupted by some other code that wants to read_trylock() this lock */ |
| | 119 | static __inline__ void arch_write_lock(arch_rwlock_t *rw) |
| | 120 | { |
| | 121 | unsigned long flags; |
| | 122 | retry: |
| | 123 | local_irq_save(flags); |
| | 124 | arch_spin_lock_flags(&rw->lock, flags); |
| | 125 | |
| | 126 | if (rw->counter != 0) { |
| | 127 | arch_spin_unlock(&rw->lock); |
| | 128 | local_irq_restore(flags); |
| | 129 | |
| | 130 | while (rw->counter != 0) |
| | 131 | cpu_relax(); |
| | 132 | |
| | 133 | goto retry; |
| | 134 | } |
| | 135 | |
| | 136 | rw->counter = -1; /* mark as write-locked */ |
| | 137 | mb(); |
| | 138 | local_irq_restore(flags); |
| | 139 | } |
| | 140 | |
| | 141 | static __inline__ void arch_write_unlock(arch_rwlock_t *rw) |
| | 142 | { |
| | 143 | rw->counter = 0; |
| | 144 | arch_spin_unlock(&rw->lock); |
| | 145 | } |
| | 146 | |
| | 147 | /* Note that we have to ensure interrupts are disabled in case we're |
| | 148 | * interrupted by some other code that wants to read_trylock() this lock */ |
| | 149 | static __inline__ int arch_write_trylock(arch_rwlock_t *rw) |
| | 150 | { |
| | 151 | unsigned long flags; |
| | 152 | int result = 0; |
| | 153 | |
| | 154 | local_irq_save(flags); |
| | 155 | if (arch_spin_trylock(&rw->lock)) { |
| | 156 | if (rw->counter == 0) { |
| | 157 | rw->counter = -1; |
| | 158 | result = 1; |
| | 159 | } else { |
| | 160 | /* Read-locked. Oh well. */ |
| | 161 | arch_spin_unlock(&rw->lock); |
| | 162 | } |
| | 163 | } |
| | 164 | local_irq_restore(flags); |
| | 165 | |
| | 166 | return result; |
| | 167 | } |
| | 168 | |
| | 169 | #endif /* __ASM_SPINLOCK_H */ |
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