1 /* spinlock.h: 32-bit Sparc spinlock support. 2 * 3 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu) 4 */ 5 6 #ifndef __SPARC_SPINLOCK_H 7 #define __SPARC_SPINLOCK_H 8 9 #ifndef __ASSEMBLY__ 10 11 #include <asm/psr.h> 12 #include <asm/barrier.h> 13 #include <asm/processor.h> /* for cpu_relax */ 14 15 #define arch_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0) 16 17 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) 18 { 19 smp_cond_load_acquire(&lock->lock, !VAL); 20 } 21 22 static inline void arch_spin_lock(arch_spinlock_t *lock) 23 { 24 __asm__ __volatile__( 25 "\n1:\n\t" 26 "ldstub [%0], %%g2\n\t" 27 "orcc %%g2, 0x0, %%g0\n\t" 28 "bne,a 2f\n\t" 29 " ldub [%0], %%g2\n\t" 30 ".subsection 2\n" 31 "2:\n\t" 32 "orcc %%g2, 0x0, %%g0\n\t" 33 "bne,a 2b\n\t" 34 " ldub [%0], %%g2\n\t" 35 "b,a 1b\n\t" 36 ".previous\n" 37 : /* no outputs */ 38 : "r" (lock) 39 : "g2", "memory", "cc"); 40 } 41 42 static inline int arch_spin_trylock(arch_spinlock_t *lock) 43 { 44 unsigned int result; 45 __asm__ __volatile__("ldstub [%1], %0" 46 : "=r" (result) 47 : "r" (lock) 48 : "memory"); 49 return (result == 0); 50 } 51 52 static inline void arch_spin_unlock(arch_spinlock_t *lock) 53 { 54 __asm__ __volatile__("stb %%g0, [%0]" : : "r" (lock) : "memory"); 55 } 56 57 /* Read-write spinlocks, allowing multiple readers 58 * but only one writer. 59 * 60 * NOTE! it is quite common to have readers in interrupts 61 * but no interrupt writers. For those circumstances we 62 * can "mix" irq-safe locks - any writer needs to get a 63 * irq-safe write-lock, but readers can get non-irqsafe 64 * read-locks. 65 * 66 * XXX This might create some problems with my dual spinlock 67 * XXX scheme, deadlocks etc. -DaveM 68 * 69 * Sort of like atomic_t's on Sparc, but even more clever. 70 * 71 * ------------------------------------ 72 * | 24-bit counter | wlock | arch_rwlock_t 73 * ------------------------------------ 74 * 31 8 7 0 75 * 76 * wlock signifies the one writer is in or somebody is updating 77 * counter. For a writer, if he successfully acquires the wlock, 78 * but counter is non-zero, he has to release the lock and wait, 79 * till both counter and wlock are zero. 80 * 81 * Unfortunately this scheme limits us to ~16,000,000 cpus. 82 */ 83 static inline void __arch_read_lock(arch_rwlock_t *rw) 84 { 85 register arch_rwlock_t *lp asm("g1"); 86 lp = rw; 87 __asm__ __volatile__( 88 "mov %%o7, %%g4\n\t" 89 "call ___rw_read_enter\n\t" 90 " ldstub [%%g1 + 3], %%g2\n" 91 : /* no outputs */ 92 : "r" (lp) 93 : "g2", "g4", "memory", "cc"); 94 } 95 96 #define arch_read_lock(lock) \ 97 do { unsigned long flags; \ 98 local_irq_save(flags); \ 99 __arch_read_lock(lock); \ 100 local_irq_restore(flags); \ 101 } while(0) 102 103 static inline void __arch_read_unlock(arch_rwlock_t *rw) 104 { 105 register arch_rwlock_t *lp asm("g1"); 106 lp = rw; 107 __asm__ __volatile__( 108 "mov %%o7, %%g4\n\t" 109 "call ___rw_read_exit\n\t" 110 " ldstub [%%g1 + 3], %%g2\n" 111 : /* no outputs */ 112 : "r" (lp) 113 : "g2", "g4", "memory", "cc"); 114 } 115 116 #define arch_read_unlock(lock) \ 117 do { unsigned long flags; \ 118 local_irq_save(flags); \ 119 __arch_read_unlock(lock); \ 120 local_irq_restore(flags); \ 121 } while(0) 122 123 static inline void arch_write_lock(arch_rwlock_t *rw) 124 { 125 register arch_rwlock_t *lp asm("g1"); 126 lp = rw; 127 __asm__ __volatile__( 128 "mov %%o7, %%g4\n\t" 129 "call ___rw_write_enter\n\t" 130 " ldstub [%%g1 + 3], %%g2\n" 131 : /* no outputs */ 132 : "r" (lp) 133 : "g2", "g4", "memory", "cc"); 134 *(volatile __u32 *)&lp->lock = ~0U; 135 } 136 137 static inline void arch_write_unlock(arch_rwlock_t *lock) 138 { 139 __asm__ __volatile__( 140 " st %%g0, [%0]" 141 : /* no outputs */ 142 : "r" (lock) 143 : "memory"); 144 } 145 146 static inline int arch_write_trylock(arch_rwlock_t *rw) 147 { 148 unsigned int val; 149 150 __asm__ __volatile__("ldstub [%1 + 3], %0" 151 : "=r" (val) 152 : "r" (&rw->lock) 153 : "memory"); 154 155 if (val == 0) { 156 val = rw->lock & ~0xff; 157 if (val) 158 ((volatile u8*)&rw->lock)[3] = 0; 159 else 160 *(volatile u32*)&rw->lock = ~0U; 161 } 162 163 return (val == 0); 164 } 165 166 static inline int __arch_read_trylock(arch_rwlock_t *rw) 167 { 168 register arch_rwlock_t *lp asm("g1"); 169 register int res asm("o0"); 170 lp = rw; 171 __asm__ __volatile__( 172 "mov %%o7, %%g4\n\t" 173 "call ___rw_read_try\n\t" 174 " ldstub [%%g1 + 3], %%g2\n" 175 : "=r" (res) 176 : "r" (lp) 177 : "g2", "g4", "memory", "cc"); 178 return res; 179 } 180 181 #define arch_read_trylock(lock) \ 182 ({ unsigned long flags; \ 183 int res; \ 184 local_irq_save(flags); \ 185 res = __arch_read_trylock(lock); \ 186 local_irq_restore(flags); \ 187 res; \ 188 }) 189 190 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) 191 #define arch_read_lock_flags(rw, flags) arch_read_lock(rw) 192 #define arch_write_lock_flags(rw, flags) arch_write_lock(rw) 193 194 #define arch_spin_relax(lock) cpu_relax() 195 #define arch_read_relax(lock) cpu_relax() 196 #define arch_write_relax(lock) cpu_relax() 197 198 #define arch_read_can_lock(rw) (!((rw)->lock & 0xff)) 199 #define arch_write_can_lock(rw) (!(rw)->lock) 200 201 #endif /* !(__ASSEMBLY__) */ 202 203 #endif /* __SPARC_SPINLOCK_H */ 204