1 /* 2 * S390 version 3 * Copyright IBM Corp. 1999 4 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) 5 * 6 * Derived from "include/asm-i386/spinlock.h" 7 */ 8 9 #ifndef __ASM_SPINLOCK_H 10 #define __ASM_SPINLOCK_H 11 12 #include <linux/smp.h> 13 14 extern int spin_retry; 15 16 static inline int 17 _raw_compare_and_swap(volatile unsigned int *lock, 18 unsigned int old, unsigned int new) 19 { 20 asm volatile( 21 " cs %0,%3,%1" 22 : "=d" (old), "=Q" (*lock) 23 : "0" (old), "d" (new), "Q" (*lock) 24 : "cc", "memory" ); 25 return old; 26 } 27 28 /* 29 * Simple spin lock operations. There are two variants, one clears IRQ's 30 * on the local processor, one does not. 31 * 32 * We make no fairness assumptions. They have a cost. 33 * 34 * (the type definitions are in asm/spinlock_types.h) 35 */ 36 37 #define arch_spin_is_locked(x) ((x)->owner_cpu != 0) 38 #define arch_spin_unlock_wait(lock) \ 39 do { while (arch_spin_is_locked(lock)) \ 40 arch_spin_relax(lock); } while (0) 41 42 extern void arch_spin_lock_wait(arch_spinlock_t *); 43 extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags); 44 extern int arch_spin_trylock_retry(arch_spinlock_t *); 45 extern void arch_spin_relax(arch_spinlock_t *lock); 46 47 static inline int arch_spin_value_unlocked(arch_spinlock_t lock) 48 { 49 return lock.owner_cpu == 0; 50 } 51 52 static inline void arch_spin_lock(arch_spinlock_t *lp) 53 { 54 int old; 55 56 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 57 if (likely(old == 0)) 58 return; 59 arch_spin_lock_wait(lp); 60 } 61 62 static inline void arch_spin_lock_flags(arch_spinlock_t *lp, 63 unsigned long flags) 64 { 65 int old; 66 67 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 68 if (likely(old == 0)) 69 return; 70 arch_spin_lock_wait_flags(lp, flags); 71 } 72 73 static inline int arch_spin_trylock(arch_spinlock_t *lp) 74 { 75 int old; 76 77 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 78 if (likely(old == 0)) 79 return 1; 80 return arch_spin_trylock_retry(lp); 81 } 82 83 static inline void arch_spin_unlock(arch_spinlock_t *lp) 84 { 85 _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0); 86 } 87 88 /* 89 * Read-write spinlocks, allowing multiple readers 90 * but only one writer. 91 * 92 * NOTE! it is quite common to have readers in interrupts 93 * but no interrupt writers. For those circumstances we 94 * can "mix" irq-safe locks - any writer needs to get a 95 * irq-safe write-lock, but readers can get non-irqsafe 96 * read-locks. 97 */ 98 99 /** 100 * read_can_lock - would read_trylock() succeed? 101 * @lock: the rwlock in question. 102 */ 103 #define arch_read_can_lock(x) ((int)(x)->lock >= 0) 104 105 /** 106 * write_can_lock - would write_trylock() succeed? 107 * @lock: the rwlock in question. 108 */ 109 #define arch_write_can_lock(x) ((x)->lock == 0) 110 111 extern void _raw_read_lock_wait(arch_rwlock_t *lp); 112 extern void _raw_read_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags); 113 extern int _raw_read_trylock_retry(arch_rwlock_t *lp); 114 extern void _raw_write_lock_wait(arch_rwlock_t *lp); 115 extern void _raw_write_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags); 116 extern int _raw_write_trylock_retry(arch_rwlock_t *lp); 117 118 static inline void arch_read_lock(arch_rwlock_t *rw) 119 { 120 unsigned int old; 121 old = rw->lock & 0x7fffffffU; 122 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old) 123 _raw_read_lock_wait(rw); 124 } 125 126 static inline void arch_read_lock_flags(arch_rwlock_t *rw, unsigned long flags) 127 { 128 unsigned int old; 129 old = rw->lock & 0x7fffffffU; 130 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old) 131 _raw_read_lock_wait_flags(rw, flags); 132 } 133 134 static inline void arch_read_unlock(arch_rwlock_t *rw) 135 { 136 unsigned int old, cmp; 137 138 old = rw->lock; 139 do { 140 cmp = old; 141 old = _raw_compare_and_swap(&rw->lock, old, old - 1); 142 } while (cmp != old); 143 } 144 145 static inline void arch_write_lock(arch_rwlock_t *rw) 146 { 147 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0)) 148 _raw_write_lock_wait(rw); 149 } 150 151 static inline void arch_write_lock_flags(arch_rwlock_t *rw, unsigned long flags) 152 { 153 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0)) 154 _raw_write_lock_wait_flags(rw, flags); 155 } 156 157 static inline void arch_write_unlock(arch_rwlock_t *rw) 158 { 159 _raw_compare_and_swap(&rw->lock, 0x80000000, 0); 160 } 161 162 static inline int arch_read_trylock(arch_rwlock_t *rw) 163 { 164 unsigned int old; 165 old = rw->lock & 0x7fffffffU; 166 if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old)) 167 return 1; 168 return _raw_read_trylock_retry(rw); 169 } 170 171 static inline int arch_write_trylock(arch_rwlock_t *rw) 172 { 173 if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)) 174 return 1; 175 return _raw_write_trylock_retry(rw); 176 } 177 178 #define arch_read_relax(lock) cpu_relax() 179 #define arch_write_relax(lock) cpu_relax() 180 181 #endif /* __ASM_SPINLOCK_H */ 182