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 void arch_spin_lock(arch_spinlock_t *lp) 48 { 49 int old; 50 51 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 52 if (likely(old == 0)) 53 return; 54 arch_spin_lock_wait(lp); 55 } 56 57 static inline void arch_spin_lock_flags(arch_spinlock_t *lp, 58 unsigned long flags) 59 { 60 int old; 61 62 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 63 if (likely(old == 0)) 64 return; 65 arch_spin_lock_wait_flags(lp, flags); 66 } 67 68 static inline int arch_spin_trylock(arch_spinlock_t *lp) 69 { 70 int old; 71 72 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id()); 73 if (likely(old == 0)) 74 return 1; 75 return arch_spin_trylock_retry(lp); 76 } 77 78 static inline void arch_spin_unlock(arch_spinlock_t *lp) 79 { 80 _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0); 81 } 82 83 /* 84 * Read-write spinlocks, allowing multiple readers 85 * but only one writer. 86 * 87 * NOTE! it is quite common to have readers in interrupts 88 * but no interrupt writers. For those circumstances we 89 * can "mix" irq-safe locks - any writer needs to get a 90 * irq-safe write-lock, but readers can get non-irqsafe 91 * read-locks. 92 */ 93 94 /** 95 * read_can_lock - would read_trylock() succeed? 96 * @lock: the rwlock in question. 97 */ 98 #define arch_read_can_lock(x) ((int)(x)->lock >= 0) 99 100 /** 101 * write_can_lock - would write_trylock() succeed? 102 * @lock: the rwlock in question. 103 */ 104 #define arch_write_can_lock(x) ((x)->lock == 0) 105 106 extern void _raw_read_lock_wait(arch_rwlock_t *lp); 107 extern void _raw_read_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags); 108 extern int _raw_read_trylock_retry(arch_rwlock_t *lp); 109 extern void _raw_write_lock_wait(arch_rwlock_t *lp); 110 extern void _raw_write_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags); 111 extern int _raw_write_trylock_retry(arch_rwlock_t *lp); 112 113 static inline void arch_read_lock(arch_rwlock_t *rw) 114 { 115 unsigned int old; 116 old = rw->lock & 0x7fffffffU; 117 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old) 118 _raw_read_lock_wait(rw); 119 } 120 121 static inline void arch_read_lock_flags(arch_rwlock_t *rw, unsigned long flags) 122 { 123 unsigned int old; 124 old = rw->lock & 0x7fffffffU; 125 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old) 126 _raw_read_lock_wait_flags(rw, flags); 127 } 128 129 static inline void arch_read_unlock(arch_rwlock_t *rw) 130 { 131 unsigned int old, cmp; 132 133 old = rw->lock; 134 do { 135 cmp = old; 136 old = _raw_compare_and_swap(&rw->lock, old, old - 1); 137 } while (cmp != old); 138 } 139 140 static inline void arch_write_lock(arch_rwlock_t *rw) 141 { 142 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0)) 143 _raw_write_lock_wait(rw); 144 } 145 146 static inline void arch_write_lock_flags(arch_rwlock_t *rw, unsigned long flags) 147 { 148 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0)) 149 _raw_write_lock_wait_flags(rw, flags); 150 } 151 152 static inline void arch_write_unlock(arch_rwlock_t *rw) 153 { 154 _raw_compare_and_swap(&rw->lock, 0x80000000, 0); 155 } 156 157 static inline int arch_read_trylock(arch_rwlock_t *rw) 158 { 159 unsigned int old; 160 old = rw->lock & 0x7fffffffU; 161 if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old)) 162 return 1; 163 return _raw_read_trylock_retry(rw); 164 } 165 166 static inline int arch_write_trylock(arch_rwlock_t *rw) 167 { 168 if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)) 169 return 1; 170 return _raw_write_trylock_retry(rw); 171 } 172 173 #define arch_read_relax(lock) cpu_relax() 174 #define arch_write_relax(lock) cpu_relax() 175 176 #endif /* __ASM_SPINLOCK_H */ 177