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/synch.h>
28 #include <asm/ppc-opcode.h>
29 #include <asm/asm-405.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 #ifdef CONFIG_PPC_PSERIES
43 #define vcpu_is_preempted vcpu_is_preempted
44 static inline bool vcpu_is_preempted(int cpu)
46 if (!firmware_has_feature(FW_FEATURE_SPLPAR))
48 return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
52 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
54 return lock.slock == 0;
57 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
60 return !arch_spin_value_unlocked(*lock);
64 * This returns the old value in the lock, so we succeeded
65 * in getting the lock if the return value is 0.
67 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
69 unsigned long tmp, token;
73 "1: " PPC_LWARX(%0,0,%2,1) "\n\
81 : "r" (token), "r" (&lock->slock)
87 static inline int arch_spin_trylock(arch_spinlock_t *lock)
89 return __arch_spin_trylock(lock) == 0;
93 * On a system with shared processors (that is, where a physical
94 * processor is multiplexed between several virtual processors),
95 * there is no point spinning on a lock if the holder of the lock
96 * isn't currently scheduled on a physical processor. Instead
97 * we detect this situation and ask the hypervisor to give the
98 * rest of our timeslice to the lock holder.
100 * So that we can tell which virtual processor is holding a lock,
101 * we put 0x80000000 | smp_processor_id() in the lock when it is
102 * held. Conveniently, we have a word in the paca that holds this
106 #if defined(CONFIG_PPC_SPLPAR)
107 /* We only yield to the hypervisor if we are in shared processor mode */
108 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
109 extern void __spin_yield(arch_spinlock_t *lock);
110 extern void __rw_yield(arch_rwlock_t *lock);
112 #define __spin_yield(x) barrier()
113 #define __rw_yield(x) barrier()
114 #define SHARED_PROCESSOR 0
117 static inline void arch_spin_lock(arch_spinlock_t *lock)
120 if (likely(__arch_spin_trylock(lock) == 0))
124 if (SHARED_PROCESSOR)
126 } while (unlikely(lock->slock != 0));
132 void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
134 unsigned long flags_dis;
137 if (likely(__arch_spin_trylock(lock) == 0))
139 local_save_flags(flags_dis);
140 local_irq_restore(flags);
143 if (SHARED_PROCESSOR)
145 } while (unlikely(lock->slock != 0));
147 local_irq_restore(flags_dis);
150 #define arch_spin_lock_flags arch_spin_lock_flags
152 static inline void arch_spin_unlock(arch_spinlock_t *lock)
154 __asm__ __volatile__("# arch_spin_unlock\n\t"
155 PPC_RELEASE_BARRIER: : :"memory");
160 * Read-write spinlocks, allowing multiple readers
161 * but only one writer.
163 * NOTE! it is quite common to have readers in interrupts
164 * but no interrupt writers. For those circumstances we
165 * can "mix" irq-safe locks - any writer needs to get a
166 * irq-safe write-lock, but readers can get non-irqsafe
171 #define __DO_SIGN_EXTEND "extsw %0,%0\n"
172 #define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
174 #define __DO_SIGN_EXTEND
175 #define WRLOCK_TOKEN (-1)
179 * This returns the old value in the lock + 1,
180 * so we got a read lock if the return value is > 0.
182 static inline long __arch_read_trylock(arch_rwlock_t *rw)
186 __asm__ __volatile__(
187 "1: " PPC_LWARX(%0,0,%1,1) "\n"
197 : "cr0", "xer", "memory");
203 * This returns the old value in the lock,
204 * so we got the write lock if the return value is 0.
206 static inline long __arch_write_trylock(arch_rwlock_t *rw)
210 token = WRLOCK_TOKEN;
211 __asm__ __volatile__(
212 "1: " PPC_LWARX(%0,0,%2,1) "\n\
220 : "r" (token), "r" (&rw->lock)
226 static inline void arch_read_lock(arch_rwlock_t *rw)
229 if (likely(__arch_read_trylock(rw) > 0))
233 if (SHARED_PROCESSOR)
235 } while (unlikely(rw->lock < 0));
240 static inline void arch_write_lock(arch_rwlock_t *rw)
243 if (likely(__arch_write_trylock(rw) == 0))
247 if (SHARED_PROCESSOR)
249 } while (unlikely(rw->lock != 0));
254 static inline int arch_read_trylock(arch_rwlock_t *rw)
256 return __arch_read_trylock(rw) > 0;
259 static inline int arch_write_trylock(arch_rwlock_t *rw)
261 return __arch_write_trylock(rw) == 0;
264 static inline void arch_read_unlock(arch_rwlock_t *rw)
268 __asm__ __volatile__(
278 : "cr0", "xer", "memory");
281 static inline void arch_write_unlock(arch_rwlock_t *rw)
283 __asm__ __volatile__("# write_unlock\n\t"
284 PPC_RELEASE_BARRIER: : :"memory");
288 #define arch_spin_relax(lock) __spin_yield(lock)
289 #define arch_read_relax(lock) __rw_yield(lock)
290 #define arch_write_relax(lock) __rw_yield(lock)
292 /* See include/linux/spinlock.h */
293 #define smp_mb__after_spinlock() smp_mb()
295 #endif /* __KERNEL__ */
296 #endif /* __ASM_SPINLOCK_H */