linux/arch/powerpc/lib/locks.c
Nicholas Piggin 20d444d06f powerpc/pseries: Move some PAPR paravirt functions to their own file
These functions will be used by the queued spinlock implementation,
and may be useful elsewhere too, so move them out of spinlock.h.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200724131423.1362108-2-npiggin@gmail.com
2020-07-26 23:34:26 +10:00

66 lines
1.7 KiB
C

// 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