summaryrefslogtreecommitdiffstats
path: root/include/asm-powerpc/spinlock.h
blob: caa4b14e0e94785910d1ad188626c654b13f10dc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H

/*
 * Simple spin 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
 *
 * Type of int is used as a full 64b word is not necessary.
 *
 * 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.
 *
 * (the type definitions are in asm/spinlock_types.h)
 */
#ifdef CONFIG_PPC64
#include <asm/paca.h>
#include <asm/hvcall.h>
#include <asm/iseries/hv_call.h>
#endif
#include <asm/asm-compat.h>
#include <asm/synch.h>

#define __raw_spin_is_locked(x)		((x)->slock != 0)

#ifdef CONFIG_PPC64
/* use 0x800000yy when locked, where yy == CPU number */
#define LOCK_TOKEN	(*(u32 *)(&get_paca()->lock_token))
#else
#define LOCK_TOKEN	1
#endif

/*
 * This returns the old value in the lock, so we succeeded
 * in getting the lock if the return value is 0.
 */
static __inline__ unsigned long __spin_trylock(raw_spinlock_t *lock)
{
	unsigned long tmp, token;

	token = LOCK_TOKEN;
	__asm__ __volatile__(
"1:	lwarx		%0,0,%2		# __spin_trylock\n\
	cmpwi		0,%0,0\n\
	bne-		2f\n\
	stwcx.		%1,0,%2\n\
	bne-		1b\n\
	isync\n\
2:"	: "=&r" (tmp)
	: "r" (token), "r" (&lock->slock)
	: "cr0", "memory");

	return tmp;
}

static int __inline__ __raw_spin_trylock(raw_spinlock_t *lock)
{
	return __spin_trylock(lock) == 0;
}

/*
 * On a system with shared processors (that is, where a physical
 * processor is multiplexed between several virtual processors),
 * there is no point spinning on a lock if the holder of the lock
 * isn't currently scheduled on a physical processor.  Instead
 * we detect this situation and ask the hypervisor to give the
 * rest of our timeslice to the lock holder.
 *
 * So that we can tell which virtual processor is holding a lock,
 * we put 0x80000000 | smp_processor_id() in the lock when it is
 * held.  Conveniently, we have a word in the paca that holds this
 * value.
 */

#if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
/* We only yield to the hypervisor if we are in shared processor mode */
#define SHARED_PROCESSOR (get_paca()->lppaca.shared_proc)
extern void __spin_yield(raw_spinlock_t *lock);
extern void __rw_yield(raw_rwlock_t *lock);
#else /* SPLPAR || ISERIES */
#define __spin_yield(x)	barrier()
#define __rw_yield(x)	barrier()
#define SHARED_PROCESSOR	0
#endif

static void __inline__ __raw_spin_lock(raw_spinlock_t *lock)
{
	while (1) {
		if (likely(__spin_trylock(lock) == 0))
			break;
		do {
			HMT_low();
			if (SHARED_PROCESSOR)
				__spin_yield(lock);
		} while (unlikely(lock->slock != 0));
		HMT_medium();
	}
}

static void __inline__ __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
{
	unsigned long flags_dis;

	while (1) {
		if (likely(__spin_trylock(lock) == 0))
			break;
		local_save_flags(flags_dis);
		local_irq_restore(flags);
		do {
			HMT_low();
			if (SHARED_PROCESSOR)
				__spin_yield(lock);
		} while (unlikely(lock->slock != 0));
		HMT_medium();
		local_irq_restore(flags_dis);
	}
}

static __inline__ void __raw_spin_unlock(raw_spinlock_t *lock)
{
	__asm__ __volatile__(SYNC_ON_SMP"	# __raw_spin_unlock"
			     : : :"memory");
	lock->slock = 0;
}

#ifdef CONFIG_PPC64
extern void __raw_spin_unlock_wait(raw_spinlock_t *lock);
#else
#define __raw_spin_unlock_wait(lock) \
	do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
#endif

/*
 * Read-write spinlocks, allowing multiple readers
 * but only one writer.
 *
 * NOTE! it is quite common to have readers in interrupts
 * but no interrupt writers. For those circumstances we
 * can "mix" irq-safe locks - any writer needs to get a
 * irq-safe write-lock, but readers can get non-irqsafe
 * read-locks.
 */

#define __raw_read_can_lock(rw)		((rw)->lock >= 0)
#define __raw_write_can_lock(rw)	(!(rw)->lock)

#ifdef CONFIG_PPC64
#define __DO_SIGN_EXTEND	"extsw	%0,%0\n"
#define WRLOCK_TOKEN		LOCK_TOKEN	/* it's negative */
#else
#define __DO_SIGN_EXTEND
#define WRLOCK_TOKEN		(-1)
#endif

/*
 * This returns the old value in the lock + 1,
 * so we got a read lock if the return value is > 0.
 */
static long __inline__ __read_trylock(raw_rwlock_t *rw)
{
	long tmp;

	__asm__ __volatile__(
"1:	lwarx		%0,0,%1		# read_trylock\n"
	__DO_SIGN_EXTEND
"	addic.		%0,%0,1\n\
	ble-		2f\n"
	PPC405_ERR77(0,%1)
"	stwcx.		%0,0,%1\n\
	bne-		1b\n\
	isync\n\
2:"	: "=&r" (tmp)
	: "r" (&rw->lock)
	: "cr0", "xer", "memory");

	return tmp;
}

/*
 * This returns the old value in the lock,
 * so we got the write lock if the return value is 0.
 */
static __inline__ long __write_trylock(raw_rwlock_t *rw)
{
	long tmp, token;

	token = WRLOCK_TOKEN;
	__asm__ __volatile__(
"1:	lwarx		%0,0,%2	# write_trylock\n\
	cmpwi		0,%0,0\n\
	bne-		2f\n"
	PPC405_ERR77(0,%1)
"	stwcx.		%1,0,%2\n\
	bne-		1b\n\
	isync\n\
2:"	: "=&r" (tmp)
	: "r" (token), "r" (&rw->lock)
	: "cr0", "memory");

	return tmp;
}

static void __inline__ __raw_read_lock(raw_rwlock_t *rw)
{
	while (1) {
		if (likely(__read_trylock(rw) > 0))
			break;
		do {
			HMT_low();
			if (SHARED_PROCESSOR)
				__rw_yield(rw);
		} while (unlikely(rw->lock < 0));
		HMT_medium();
	}
}

static void __inline__ __raw_write_lock(raw_rwlock_t *rw)
{
	while (1) {
		if (likely(__write_trylock(rw) == 0))
			break;
		do {
			HMT_low();
			if (SHARED_PROCESSOR)
				__rw_yield(rw);
		} while (unlikely(rw->lock != 0));
		HMT_medium();
	}
}

static int __inline__ __raw_read_trylock(raw_rwlock_t *rw)
{
	return __read_trylock(rw) > 0;
}

static int __inline__ __raw_write_trylock(raw_rwlock_t *rw)
{
	return __write_trylock(rw) == 0;
}

static void __inline__ __raw_read_unlock(raw_rwlock_t *rw)
{
	long tmp;

	__asm__ __volatile__(
	"eieio				# read_unlock\n\
1:	lwarx		%0,0,%1\n\
	addic		%0,%0,-1\n"
	PPC405_ERR77(0,%1)
"	stwcx.		%0,0,%1\n\
	bne-		1b"
	: "=&r"(tmp)
	: "r"(&rw->lock)
	: "cr0", "memory");
}

static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
{
	__asm__ __volatile__(SYNC_ON_SMP"	# write_unlock"
			     : : :"memory");
	rw->lock = 0;
}

#endif /* __ASM_SPINLOCK_H */