347 lines
7.7 KiB
C
347 lines
7.7 KiB
C
#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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#ifdef __KERNEL__
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/*
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* Simple spin lock operations.
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*
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* Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
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* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
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* Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
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* Rework to support virtual processors
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*
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* Type of int is used as a full 64b word is not necessary.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* (the type definitions are in asm/spinlock_types.h)
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*/
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#include <linux/irqflags.h>
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#ifdef CONFIG_PPC64
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#include <asm/paca.h>
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#include <asm/hvcall.h>
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#endif
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#include <asm/asm-compat.h>
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#include <asm/synch.h>
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#include <asm/ppc-opcode.h>
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#ifdef CONFIG_PPC64
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/* use 0x800000yy when locked, where yy == CPU number */
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#ifdef __BIG_ENDIAN__
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#define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
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#else
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#define LOCK_TOKEN (*(u32 *)(&get_paca()->paca_index))
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#endif
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#else
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#define LOCK_TOKEN 1
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#endif
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#if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
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#define CLEAR_IO_SYNC (get_paca()->io_sync = 0)
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#define SYNC_IO do { \
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if (unlikely(get_paca()->io_sync)) { \
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mb(); \
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get_paca()->io_sync = 0; \
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} \
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} while (0)
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#else
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#define CLEAR_IO_SYNC
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#define SYNC_IO
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#endif
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#ifdef CONFIG_PPC_PSERIES
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#define vcpu_is_preempted vcpu_is_preempted
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static inline bool vcpu_is_preempted(int cpu)
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{
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return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
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}
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#endif
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static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
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{
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return lock.slock == 0;
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}
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static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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smp_mb();
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return !arch_spin_value_unlocked(*lock);
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}
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/*
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* This returns the old value in the lock, so we succeeded
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* in getting the lock if the return value is 0.
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*/
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static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned long tmp, token;
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token = LOCK_TOKEN;
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__asm__ __volatile__(
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"1: " PPC_LWARX(%0,0,%2,1) "\n\
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cmpwi 0,%0,0\n\
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bne- 2f\n\
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stwcx. %1,0,%2\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:"
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: "=&r" (tmp)
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: "r" (token), "r" (&lock->slock)
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: "cr0", "memory");
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return tmp;
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}
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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CLEAR_IO_SYNC;
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return __arch_spin_trylock(lock) == 0;
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}
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/*
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* On a system with shared processors (that is, where a physical
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* processor is multiplexed between several virtual processors),
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* there is no point spinning on a lock if the holder of the lock
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* isn't currently scheduled on a physical processor. Instead
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* we detect this situation and ask the hypervisor to give the
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* rest of our timeslice to the lock holder.
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*
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* So that we can tell which virtual processor is holding a lock,
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* we put 0x80000000 | smp_processor_id() in the lock when it is
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* held. Conveniently, we have a word in the paca that holds this
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* value.
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*/
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#if defined(CONFIG_PPC_SPLPAR)
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/* We only yield to the hypervisor if we are in shared processor mode */
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#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
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extern void __spin_yield(arch_spinlock_t *lock);
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extern void __rw_yield(arch_rwlock_t *lock);
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#else /* SPLPAR */
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#define __spin_yield(x) barrier()
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#define __rw_yield(x) barrier()
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#define SHARED_PROCESSOR 0
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#endif
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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CLEAR_IO_SYNC;
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while (1) {
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if (likely(__arch_spin_trylock(lock) == 0))
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break;
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do {
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HMT_low();
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if (SHARED_PROCESSOR)
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__spin_yield(lock);
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} while (unlikely(lock->slock != 0));
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HMT_medium();
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}
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}
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static inline
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void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
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{
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unsigned long flags_dis;
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CLEAR_IO_SYNC;
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while (1) {
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if (likely(__arch_spin_trylock(lock) == 0))
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break;
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local_save_flags(flags_dis);
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local_irq_restore(flags);
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do {
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HMT_low();
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if (SHARED_PROCESSOR)
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__spin_yield(lock);
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} while (unlikely(lock->slock != 0));
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HMT_medium();
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local_irq_restore(flags_dis);
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}
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}
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static inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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SYNC_IO;
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__asm__ __volatile__("# arch_spin_unlock\n\t"
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PPC_RELEASE_BARRIER: : :"memory");
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lock->slock = 0;
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}
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static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
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{
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arch_spinlock_t lock_val;
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smp_mb();
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/*
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* Atomically load and store back the lock value (unchanged). This
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* ensures that our observation of the lock value is ordered with
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* respect to other lock operations.
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*/
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__asm__ __volatile__(
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"1: " PPC_LWARX(%0, 0, %2, 0) "\n"
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" stwcx. %0, 0, %2\n"
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" bne- 1b\n"
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: "=&r" (lock_val), "+m" (*lock)
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: "r" (lock)
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: "cr0", "xer");
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if (arch_spin_value_unlocked(lock_val))
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goto out;
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while (lock->slock) {
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HMT_low();
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if (SHARED_PROCESSOR)
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__spin_yield(lock);
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}
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HMT_medium();
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out:
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smp_mb();
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*/
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#define arch_read_can_lock(rw) ((rw)->lock >= 0)
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#define arch_write_can_lock(rw) (!(rw)->lock)
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#ifdef CONFIG_PPC64
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#define __DO_SIGN_EXTEND "extsw %0,%0\n"
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#define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
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#else
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#define __DO_SIGN_EXTEND
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#define WRLOCK_TOKEN (-1)
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#endif
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/*
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* This returns the old value in the lock + 1,
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* so we got a read lock if the return value is > 0.
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*/
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static inline long __arch_read_trylock(arch_rwlock_t *rw)
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{
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long tmp;
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__asm__ __volatile__(
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"1: " PPC_LWARX(%0,0,%1,1) "\n"
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__DO_SIGN_EXTEND
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" addic. %0,%0,1\n\
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ble- 2f\n"
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PPC405_ERR77(0,%1)
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" stwcx. %0,0,%1\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:" : "=&r" (tmp)
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: "r" (&rw->lock)
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: "cr0", "xer", "memory");
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return tmp;
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}
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/*
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* This returns the old value in the lock,
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* so we got the write lock if the return value is 0.
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*/
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static inline long __arch_write_trylock(arch_rwlock_t *rw)
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{
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long tmp, token;
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token = WRLOCK_TOKEN;
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__asm__ __volatile__(
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"1: " PPC_LWARX(%0,0,%2,1) "\n\
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cmpwi 0,%0,0\n\
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bne- 2f\n"
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PPC405_ERR77(0,%1)
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" stwcx. %1,0,%2\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:" : "=&r" (tmp)
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: "r" (token), "r" (&rw->lock)
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: "cr0", "memory");
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return tmp;
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}
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static inline void arch_read_lock(arch_rwlock_t *rw)
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{
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while (1) {
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if (likely(__arch_read_trylock(rw) > 0))
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break;
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do {
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HMT_low();
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if (SHARED_PROCESSOR)
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__rw_yield(rw);
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} while (unlikely(rw->lock < 0));
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HMT_medium();
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}
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}
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static inline void arch_write_lock(arch_rwlock_t *rw)
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{
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while (1) {
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if (likely(__arch_write_trylock(rw) == 0))
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break;
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do {
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HMT_low();
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if (SHARED_PROCESSOR)
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__rw_yield(rw);
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} while (unlikely(rw->lock != 0));
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HMT_medium();
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}
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}
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static inline int arch_read_trylock(arch_rwlock_t *rw)
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{
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return __arch_read_trylock(rw) > 0;
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}
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static inline int arch_write_trylock(arch_rwlock_t *rw)
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{
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return __arch_write_trylock(rw) == 0;
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}
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static inline void arch_read_unlock(arch_rwlock_t *rw)
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{
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long tmp;
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__asm__ __volatile__(
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"# read_unlock\n\t"
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PPC_RELEASE_BARRIER
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"1: lwarx %0,0,%1\n\
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addic %0,%0,-1\n"
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PPC405_ERR77(0,%1)
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" stwcx. %0,0,%1\n\
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bne- 1b"
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: "=&r"(tmp)
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: "r"(&rw->lock)
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: "cr0", "xer", "memory");
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}
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static inline void arch_write_unlock(arch_rwlock_t *rw)
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{
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__asm__ __volatile__("# write_unlock\n\t"
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PPC_RELEASE_BARRIER: : :"memory");
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rw->lock = 0;
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}
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#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
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#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
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#define arch_spin_relax(lock) __spin_yield(lock)
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#define arch_read_relax(lock) __rw_yield(lock)
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#define arch_write_relax(lock) __rw_yield(lock)
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#endif /* __KERNEL__ */
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#endif /* __ASM_SPINLOCK_H */
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