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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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
*/
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/smp.h>
/* waiting for a spinlock... */
#if defined(CONFIG_PPC_SPLPAR)
#include <asm/hvcall.h>
#include <asm/smp.h>
void splpar_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 = yield_count_of(holder_cpu);
if ((yield_count & 1) == 0)
return; /* virtual cpu is currently running */
rmb();
if (lock->slock != lock_value)
return; /* something has changed */
yield_to_preempted(holder_cpu, yield_count);
}
EXPORT_SYMBOL_GPL(splpar_spin_yield);
/*
* 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 splpar_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 = yield_count_of(holder_cpu);
if ((yield_count & 1) == 0)
return; /* virtual cpu is currently running */
rmb();
if (rw->lock != lock_value)
return; /* something has changed */
yield_to_preempted(holder_cpu, yield_count);
}
#endif
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