locks.c
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/*
* Spin and read/write lock operations.
*
* Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
* Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
* Rework to support virtual processors
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/stringify.h>
#include <linux/smp.h>
/* waiting for a spinlock... */
#if defined(CONFIG_PPC_SPLPAR)
#include <asm/hvcall.h>
#include <asm/smp.h>
void __spin_yield(arch_spinlock_t *lock)
{
unsigned int lock_value, holder_cpu, yield_count;
lock_value = lock->slock;
if (lock_value == 0)
return;
holder_cpu = lock_value & 0xffff;
BUG_ON(holder_cpu >= NR_CPUS);
yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
if ((yield_count & 1) == 0)
return; /* virtual cpu is currently running */
rmb();
if (lock->slock != lock_value)
return; /* something has changed */
plpar_hcall_norets(H_CONFER,
get_hard_smp_processor_id(holder_cpu), yield_count);
}
/*
* Waiting for a read lock or a write lock on a rwlock...
* This turns out to be the same for read and write locks, since
* we only know the holder if it is write-locked.
*/
void __rw_yield(arch_rwlock_t *rw)
{
int lock_value;
unsigned int holder_cpu, yield_count;
lock_value = rw->lock;
if (lock_value >= 0)
return; /* no write lock at present */
holder_cpu = lock_value & 0xffff;
BUG_ON(holder_cpu >= NR_CPUS);
yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
if ((yield_count & 1) == 0)
return; /* virtual cpu is currently running */
rmb();
if (rw->lock != lock_value)
return; /* something has changed */
plpar_hcall_norets(H_CONFER,
get_hard_smp_processor_id(holder_cpu), yield_count);
}
#endif
void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
smp_mb();
while (lock->slock) {
HMT_low();
if (SHARED_PROCESSOR)
__spin_yield(lock);
}
HMT_medium();
smp_mb();
}
EXPORT_SYMBOL(arch_spin_unlock_wait);