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

 
 1/*
 2 * Spin and read/write lock operations.
 3 *
 4 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
 5 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
 6 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
 7 *   Rework to support virtual processors
 8 *
 9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
13 */
14
15#include <linux/kernel.h>
16#include <linux/spinlock.h>
17#include <linux/export.h>
18#include <linux/stringify.h>
19#include <linux/smp.h>
20
21/* waiting for a spinlock... */
22#if defined(CONFIG_PPC_SPLPAR)
23#include <asm/hvcall.h>
24#include <asm/smp.h>
25
26void __spin_yield(arch_spinlock_t *lock)
27{
28	unsigned int lock_value, holder_cpu, yield_count;
29
30	lock_value = lock->slock;
31	if (lock_value == 0)
32		return;
33	holder_cpu = lock_value & 0xffff;
34	BUG_ON(holder_cpu >= NR_CPUS);
35	yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
 
36	if ((yield_count & 1) == 0)
37		return;		/* virtual cpu is currently running */
38	rmb();
39	if (lock->slock != lock_value)
40		return;		/* something has changed */
41	plpar_hcall_norets(H_CONFER,
42		get_hard_smp_processor_id(holder_cpu), yield_count);
43}
44EXPORT_SYMBOL_GPL(__spin_yield);
45
46/*
47 * Waiting for a read lock or a write lock on a rwlock...
48 * This turns out to be the same for read and write locks, since
49 * we only know the holder if it is write-locked.
50 */
51void __rw_yield(arch_rwlock_t *rw)
52{
53	int lock_value;
54	unsigned int holder_cpu, yield_count;
55
56	lock_value = rw->lock;
57	if (lock_value >= 0)
58		return;		/* no write lock at present */
59	holder_cpu = lock_value & 0xffff;
60	BUG_ON(holder_cpu >= NR_CPUS);
61	yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
 
62	if ((yield_count & 1) == 0)
63		return;		/* virtual cpu is currently running */
64	rmb();
65	if (rw->lock != lock_value)
66		return;		/* something has changed */
67	plpar_hcall_norets(H_CONFER,
68		get_hard_smp_processor_id(holder_cpu), yield_count);
69}
70#endif
71
72void arch_spin_unlock_wait(arch_spinlock_t *lock)
73{
74	smp_mb();
75
76	while (lock->slock) {
77		HMT_low();
78		if (SHARED_PROCESSOR)
79			__spin_yield(lock);
80	}
81	HMT_medium();
82
83	smp_mb();
84}
85
86EXPORT_SYMBOL(arch_spin_unlock_wait);