1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Spin and read/write lock operations.
4 *
5 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
6 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
7 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
8 *   Rework to support virtual processors
9 */
10
11#include <linux/kernel.h>
12#include <linux/spinlock.h>
13#include <linux/export.h>
14#include <linux/smp.h>
15
16/* waiting for a spinlock... */
17#if defined(CONFIG_PPC_SPLPAR)
18#include <asm/hvcall.h>
19#include <asm/smp.h>
20
21void splpar_spin_yield(arch_spinlock_t *lock)
22{
23	unsigned int lock_value, holder_cpu, yield_count;
24
25	lock_value = lock->slock;
26	if (lock_value == 0)
27		return;
28	holder_cpu = lock_value & 0xffff;
29	BUG_ON(holder_cpu >= NR_CPUS);
30
31	yield_count = yield_count_of(holder_cpu);
32	if ((yield_count & 1) == 0)
33		return;		/* virtual cpu is currently running */
34	rmb();
35	if (lock->slock != lock_value)
36		return;		/* something has changed */
37	yield_to_preempted(holder_cpu, yield_count);
38}
39EXPORT_SYMBOL_GPL(splpar_spin_yield);
40
41/*
42 * Waiting for a read lock or a write lock on a rwlock...
43 * This turns out to be the same for read and write locks, since
44 * we only know the holder if it is write-locked.
45 */
46void splpar_rw_yield(arch_rwlock_t *rw)
47{
48	int lock_value;
49	unsigned int holder_cpu, yield_count;
50
51	lock_value = rw->lock;
52	if (lock_value >= 0)
53		return;		/* no write lock at present */
54	holder_cpu = lock_value & 0xffff;
55	BUG_ON(holder_cpu >= NR_CPUS);
56
57	yield_count = yield_count_of(holder_cpu);
58	if ((yield_count & 1) == 0)
59		return;		/* virtual cpu is currently running */
60	rmb();
61	if (rw->lock != lock_value)
62		return;		/* something has changed */
63	yield_to_preempted(holder_cpu, yield_count);
64}
65#endif
66