1 #ifndef __ASM_SPINLOCK_H
2 #define __ASM_SPINLOCK_H
6 * Simple spin lock operations.
8 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
9 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
10 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
11 * Rework to support virtual processors
13 * Type of int is used as a full 64b word is not necessary.
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version
18 * 2 of the License, or (at your option) any later version.
20 * (the type definitions are in asm/spinlock_types.h)
22 #include <linux/irqflags.h>
25 #include <asm/hvcall.h>
27 #include <asm/asm-compat.h>
28 #include <asm/synch.h>
29 #include <asm/ppc-opcode.h>
32 /* use 0x800000yy when locked, where yy == CPU number */
34 #define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
36 #define LOCK_TOKEN (*(u32 *)(&get_paca()->paca_index))
42 #if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
43 #define CLEAR_IO_SYNC (get_paca()->io_sync = 0)
44 #define SYNC_IO do { \
45 if (unlikely(get_paca()->io_sync)) { \
47 get_paca()->io_sync = 0; \
55 #ifdef CONFIG_PPC_PSERIES
56 #define vcpu_is_preempted vcpu_is_preempted
57 static inline bool vcpu_is_preempted(int cpu)
59 return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
63 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
65 return lock.slock == 0;
68 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
71 return !arch_spin_value_unlocked(*lock);
75 * This returns the old value in the lock, so we succeeded
76 * in getting the lock if the return value is 0.
78 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
80 unsigned long tmp, token;
84 "1: " PPC_LWARX(%0,0,%2,1) "\n\
92 : "r" (token), "r" (&lock->slock)
98 static inline int arch_spin_trylock(arch_spinlock_t *lock)
101 return __arch_spin_trylock(lock) == 0;
105 * On a system with shared processors (that is, where a physical
106 * processor is multiplexed between several virtual processors),
107 * there is no point spinning on a lock if the holder of the lock
108 * isn't currently scheduled on a physical processor. Instead
109 * we detect this situation and ask the hypervisor to give the
110 * rest of our timeslice to the lock holder.
112 * So that we can tell which virtual processor is holding a lock,
113 * we put 0x80000000 | smp_processor_id() in the lock when it is
114 * held. Conveniently, we have a word in the paca that holds this
118 #if defined(CONFIG_PPC_SPLPAR)
119 /* We only yield to the hypervisor if we are in shared processor mode */
120 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
121 extern void __spin_yield(arch_spinlock_t *lock);
122 extern void __rw_yield(arch_rwlock_t *lock);
124 #define __spin_yield(x) barrier()
125 #define __rw_yield(x) barrier()
126 #define SHARED_PROCESSOR 0
129 static inline void arch_spin_lock(arch_spinlock_t *lock)
133 if (likely(__arch_spin_trylock(lock) == 0))
137 if (SHARED_PROCESSOR)
139 } while (unlikely(lock->slock != 0));
145 void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
147 unsigned long flags_dis;
151 if (likely(__arch_spin_trylock(lock) == 0))
153 local_save_flags(flags_dis);
154 local_irq_restore(flags);
157 if (SHARED_PROCESSOR)
159 } while (unlikely(lock->slock != 0));
161 local_irq_restore(flags_dis);
165 static inline void arch_spin_unlock(arch_spinlock_t *lock)
168 __asm__ __volatile__("# arch_spin_unlock\n\t"
169 PPC_RELEASE_BARRIER: : :"memory");
174 * Read-write spinlocks, allowing multiple readers
175 * but only one writer.
177 * NOTE! it is quite common to have readers in interrupts
178 * but no interrupt writers. For those circumstances we
179 * can "mix" irq-safe locks - any writer needs to get a
180 * irq-safe write-lock, but readers can get non-irqsafe
184 #define arch_read_can_lock(rw) ((rw)->lock >= 0)
185 #define arch_write_can_lock(rw) (!(rw)->lock)
188 #define __DO_SIGN_EXTEND "extsw %0,%0\n"
189 #define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
191 #define __DO_SIGN_EXTEND
192 #define WRLOCK_TOKEN (-1)
196 * This returns the old value in the lock + 1,
197 * so we got a read lock if the return value is > 0.
199 static inline long __arch_read_trylock(arch_rwlock_t *rw)
203 __asm__ __volatile__(
204 "1: " PPC_LWARX(%0,0,%1,1) "\n"
214 : "cr0", "xer", "memory");
220 * This returns the old value in the lock,
221 * so we got the write lock if the return value is 0.
223 static inline long __arch_write_trylock(arch_rwlock_t *rw)
227 token = WRLOCK_TOKEN;
228 __asm__ __volatile__(
229 "1: " PPC_LWARX(%0,0,%2,1) "\n\
237 : "r" (token), "r" (&rw->lock)
243 static inline void arch_read_lock(arch_rwlock_t *rw)
246 if (likely(__arch_read_trylock(rw) > 0))
250 if (SHARED_PROCESSOR)
252 } while (unlikely(rw->lock < 0));
257 static inline void arch_write_lock(arch_rwlock_t *rw)
260 if (likely(__arch_write_trylock(rw) == 0))
264 if (SHARED_PROCESSOR)
266 } while (unlikely(rw->lock != 0));
271 static inline int arch_read_trylock(arch_rwlock_t *rw)
273 return __arch_read_trylock(rw) > 0;
276 static inline int arch_write_trylock(arch_rwlock_t *rw)
278 return __arch_write_trylock(rw) == 0;
281 static inline void arch_read_unlock(arch_rwlock_t *rw)
285 __asm__ __volatile__(
295 : "cr0", "xer", "memory");
298 static inline void arch_write_unlock(arch_rwlock_t *rw)
300 __asm__ __volatile__("# write_unlock\n\t"
301 PPC_RELEASE_BARRIER: : :"memory");
305 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
306 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
308 #define arch_spin_relax(lock) __spin_yield(lock)
309 #define arch_read_relax(lock) __rw_yield(lock)
310 #define arch_write_relax(lock) __rw_yield(lock)
312 /* See include/linux/spinlock.h */
313 #define smp_mb__after_spinlock() smp_mb()
315 #endif /* __KERNEL__ */
316 #endif /* __ASM_SPINLOCK_H */