![Paul Mackerras](/assets/img/avatar_default.png)
This changes the writeX family of functions to have a sync instruction before the MMIO store rather than after, because the generally expected behaviour is that the device receiving the MMIO store can be guaranteed to see the effects of any preceding writes to normal memory. To preserve ordering between writeX and readX, and to preserve ordering between preceding stores and the readX, the readX family of functions have had an sync added before the load. Although writeX followed by spin_unlock is not officially guaranteed to keep the writeX inside the spin-locked region unless an mmiowb() is used, there are currently drivers that depend on the previous behaviour on powerpc, which was that the mmiowb wasn't actually required. Therefore we have a per-cpu flag that is set by writeX, cleared by __raw_spin_lock and mmiowb, and tested by __raw_spin_unlock. If it is set, __raw_spin_unlock does a sync and clears it. This changes both 32-bit and 64-bit readX/writeX. 32-bit already has a sync in __raw_spin_unlock (since lwsync doesn't exist on 32-bit), and thus doesn't need the per-cpu flag. Tested on G5 (PPC970) and POWER5. Signed-off-by: Paul Mackerras <paulus@samba.org>
290 lines
6.5 KiB
C
290 lines
6.5 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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#ifdef CONFIG_PPC64
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#include <asm/paca.h>
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#include <asm/hvcall.h>
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#include <asm/iseries/hv_call.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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#define __raw_spin_is_locked(x) ((x)->slock != 0)
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#ifdef CONFIG_PPC64
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/* use 0x800000yy when locked, where yy == CPU number */
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#define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
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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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/*
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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 __spin_trylock(raw_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: lwarx %0,0,%2\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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isync\n\
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2:" : "=&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 int __inline__ __raw_spin_trylock(raw_spinlock_t *lock)
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{
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CLEAR_IO_SYNC;
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return __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) || defined(CONFIG_PPC_ISERIES)
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/* We only yield to the hypervisor if we are in shared processor mode */
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#define SHARED_PROCESSOR (get_lppaca()->shared_proc)
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extern void __spin_yield(raw_spinlock_t *lock);
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extern void __rw_yield(raw_rwlock_t *lock);
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#else /* SPLPAR || ISERIES */
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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 void __inline__ __raw_spin_lock(raw_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(__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 void __inline__ __raw_spin_lock_flags(raw_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(__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 __raw_spin_unlock(raw_spinlock_t *lock)
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{
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SYNC_IO;
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__asm__ __volatile__("# __raw_spin_unlock\n\t"
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LWSYNC_ON_SMP: : :"memory");
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lock->slock = 0;
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}
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#ifdef CONFIG_PPC64
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extern void __raw_spin_unlock_wait(raw_spinlock_t *lock);
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#else
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#define __raw_spin_unlock_wait(lock) \
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do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
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#endif
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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 __raw_read_can_lock(rw) ((rw)->lock >= 0)
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#define __raw_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 long __inline__ __read_trylock(raw_rwlock_t *rw)
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{
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long tmp;
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__asm__ __volatile__(
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"1: lwarx %0,0,%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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isync\n\
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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 __write_trylock(raw_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: lwarx %0,0,%2\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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isync\n\
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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 void __inline__ __raw_read_lock(raw_rwlock_t *rw)
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{
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while (1) {
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if (likely(__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 void __inline__ __raw_write_lock(raw_rwlock_t *rw)
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{
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while (1) {
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if (likely(__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 int __inline__ __raw_read_trylock(raw_rwlock_t *rw)
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{
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return __read_trylock(rw) > 0;
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}
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static int __inline__ __raw_write_trylock(raw_rwlock_t *rw)
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{
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return __write_trylock(rw) == 0;
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}
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static void __inline__ __raw_read_unlock(raw_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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LWSYNC_ON_SMP
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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", "memory");
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}
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static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
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{
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__asm__ __volatile__("# write_unlock\n\t"
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LWSYNC_ON_SMP: : :"memory");
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rw->lock = 0;
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}
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#endif /* __KERNEL__ */
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#endif /* __ASM_SPINLOCK_H */
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