summaryrefslogtreecommitdiff
path: root/arch/arc/include/asm/spinlock.h
blob: ce9bfcf1d87085035f75d582964308f874ed5fa4 (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
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
/*
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H

#include <asm/spinlock_types.h>
#include <asm/processor.h>
#include <asm/barrier.h>

#define arch_spin_is_locked(x)	((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
#define arch_spin_lock_flags(lock, flags)	arch_spin_lock(lock)

#ifdef CONFIG_ARC_HAS_LLSC

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
	unsigned int val;

	smp_mb();

	__asm__ __volatile__(
	"1:	llock	%[val], [%[slock]]	\n"
	"	breq	%[val], %[LOCKED], 1b	\n"	/* spin while LOCKED */
	"	scond	%[LOCKED], [%[slock]]	\n"	/* acquire */
	"	bnz	1b			\n"
	"					\n"
	: [val]		"=&r"	(val)
	: [slock]	"r"	(&(lock->slock)),
	  [LOCKED]	"r"	(__ARCH_SPIN_LOCK_LOCKED__)
	: "memory", "cc");

	smp_mb();
}

/* 1 - lock taken successfully */
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1:	llock	%[val], [%[slock]]	\n"
	"	breq	%[val], %[LOCKED], 4f	\n"	/* already LOCKED, just bail */
	"	scond	%[LOCKED], [%[slock]]	\n"	/* acquire */
	"	bnz	1b			\n"
	"	mov	%[got_it], 1		\n"
	"4:					\n"
	"					\n"
	: [val]		"=&r"	(val),
	  [got_it]	"+&r"	(got_it)
	: [slock]	"r"	(&(lock->slock)),
	  [LOCKED]	"r"	(__ARCH_SPIN_LOCK_LOCKED__)
	: "memory", "cc");

	smp_mb();

	return got_it;
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
	smp_mb();

	lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;

	smp_mb();
}

/*
 * Read-write spinlocks, allowing multiple readers but only one writer.
 * Unfair locking as Writers could be starved indefinitely by Reader(s)
 */

static inline void arch_read_lock(arch_rwlock_t *rw)
{
	unsigned int val;

	smp_mb();

	/*
	 * zero means writer holds the lock exclusively, deny Reader.
	 * Otherwise grant lock to first/subseq reader
	 *
	 * 	if (rw->counter > 0) {
	 *		rw->counter--;
	 *		ret = 1;
	 *	}
	 */

	__asm__ __volatile__(
	"1:	llock	%[val], [%[rwlock]]	\n"
	"	brls	%[val], %[WR_LOCKED], 1b\n"	/* <= 0: spin while write locked */
	"	sub	%[val], %[val], 1	\n"	/* reader lock */
	"	scond	%[val], [%[rwlock]]	\n"
	"	bnz	1b			\n"
	"					\n"
	: [val]		"=&r"	(val)
	: [rwlock]	"r"	(&(rw->counter)),
	  [WR_LOCKED]	"ir"	(0)
	: "memory", "cc");

	smp_mb();
}

/* 1 - lock taken successfully */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1:	llock	%[val], [%[rwlock]]	\n"
	"	brls	%[val], %[WR_LOCKED], 4f\n"	/* <= 0: already write locked, bail */
	"	sub	%[val], %[val], 1	\n"	/* counter-- */
	"	scond	%[val], [%[rwlock]]	\n"
	"	bnz	1b			\n"	/* retry if collided with someone */
	"	mov	%[got_it], 1		\n"
	"					\n"
	"4: ; --- done ---			\n"

	: [val]		"=&r"	(val),
	  [got_it]	"+&r"	(got_it)
	: [rwlock]	"r"	(&(rw->counter)),
	  [WR_LOCKED]	"ir"	(0)
	: "memory", "cc");

	smp_mb();

	return got_it;
}

static inline void arch_write_lock(arch_rwlock_t *rw)
{
	unsigned int val;

	smp_mb();

	/*
	 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
	 * deny writer. Otherwise if unlocked grant to writer
	 * Hence the claim that Linux rwlocks are unfair to writers.
	 * (can be starved for an indefinite time by readers).
	 *
	 *	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
	 *		rw->counter = 0;
	 *		ret = 1;
	 *	}
	 */

	__asm__ __volatile__(
	"1:	llock	%[val], [%[rwlock]]	\n"
	"	brne	%[val], %[UNLOCKED], 1b	\n"	/* while !UNLOCKED spin */
	"	mov	%[val], %[WR_LOCKED]	\n"
	"	scond	%[val], [%[rwlock]]	\n"
	"	bnz	1b			\n"
	"					\n"
	: [val]		"=&r"	(val)
	: [rwlock]	"r"	(&(rw->counter)),
	  [UNLOCKED]	"ir"	(__ARCH_RW_LOCK_UNLOCKED__),
	  [WR_LOCKED]	"ir"	(0)
	: "memory", "cc");

	smp_mb();
}

/* 1 - lock taken successfully */
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
	unsigned int val, got_it = 0;

	smp_mb();

	__asm__ __volatile__(
	"1:	llock	%[val], [%[rwlock]]	\n"
	"	brne	%[val], %[UNLOCKED], 4f	\n"	/* !UNLOCKED, bail */
	"	mov	%[val], %[WR_LOCKED]	\n"
	"	scond	%[val], [%[rwlock]]	\n"
	"	bnz	1b			\n"	/* retry if collided with someone */
	"	mov	%[got_it], 1		\n"
	"					\n"
	"4: ; --- done ---			\n"

	: [val]		"=&r"	(val),
	  [got_it]	"+&r"	(got_it)
	: [rwlock]	"r"	(&(rw->counter)),
	  [UNLOCKED]	"ir"	(__ARCH_RW_LOCK_UNLOCKED__),
	  [WR_LOCKED]	"ir"	(0)
	: "memory", "cc");

	smp_mb();

	return got_it;
}

static inline void arch_read_unlock(arch_rwlock_t *rw)
{
	unsigned int val;

	smp_mb();

	/*
	 * rw->counter++;
	 */
	__asm__ __volatile__(
	"1:	llock	%[val], [%[rwlock]]	\n"
	"	add	%[val], %[val], 1	\n"
	"	scond	%[val], [%[rwlock]]	\n"
	"	bnz	1b			\n"
	"					\n"
	: [val]		"=&r"	(val)
	: [rwlock]	"r"	(&(rw->counter))
	: "memory", "cc");

	smp_mb();
}

static inline void arch_write_unlock(arch_rwlock_t *rw)
{
	smp_mb();

	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;

	smp_mb();
}

#else	/* !CONFIG_ARC_HAS_LLSC */

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

	/*
	 * This smp_mb() is technically superfluous, we only need the one
	 * after the lock for providing the ACQUIRE semantics.
	 * However doing the "right" thing was regressing hackbench
	 * so keeping this, pending further investigation
	 */
	smp_mb();

	__asm__ __volatile__(
	"1:	ex  %0, [%1]		\n"
#ifdef CONFIG_EZNPS_MTM_EXT
	"	.word %3		\n"
#endif
	"	breq  %0, %2, 1b	\n"
	: "+&r" (val)
	: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
#ifdef CONFIG_EZNPS_MTM_EXT
	, "i"(CTOP_INST_SCHD_RW)
#endif
	: "memory");

	/*
	 * ACQUIRE barrier to ensure load/store after taking the lock
	 * don't "bleed-up" out of the critical section (leak-in is allowed)
	 * http://www.spinics.net/lists/kernel/msg2010409.html
	 *
	 * ARCv2 only has load-load, store-store and all-all barrier
	 * thus need the full all-all barrier
	 */
	smp_mb();
}

/* 1 - lock taken successfully */
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
	unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;

	smp_mb();

	__asm__ __volatile__(
	"1:	ex  %0, [%1]		\n"
	: "+r" (val)
	: "r"(&(lock->slock))
	: "memory");

	smp_mb();

	return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
	unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;

	/*
	 * RELEASE barrier: given the instructions avail on ARCv2, full barrier
	 * is the only option
	 */
	smp_mb();

	/*
	 * EX is not really required here, a simple STore of 0 suffices.
	 * However this causes tasklist livelocks in SystemC based SMP virtual
	 * platforms where the systemc core scheduler uses EX as a cue for
	 * moving to next core. Do a git log of this file for details
	 */
	__asm__ __volatile__(
	"	ex  %0, [%1]		\n"
	: "+r" (val)
	: "r"(&(lock->slock))
	: "memory");

	/*
	 * superfluous, but keeping for now - see pairing version in
	 * arch_spin_lock above
	 */
	smp_mb();
}

/*
 * Read-write spinlocks, allowing multiple readers but only one writer.
 * Unfair locking as Writers could be starved indefinitely by Reader(s)
 *
 * The spinlock itself is contained in @counter and access to it is
 * serialized with @lock_mutex.
 */

/* 1 - lock taken successfully */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
	int ret = 0;
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));

	/*
	 * zero means writer holds the lock exclusively, deny Reader.
	 * Otherwise grant lock to first/subseq reader
	 */
	if (rw->counter > 0) {
		rw->counter--;
		ret = 1;
	}

	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);

	smp_mb();
	return ret;
}

/* 1 - lock taken successfully */
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
	int ret = 0;
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));

	/*
	 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
	 * deny writer. Otherwise if unlocked grant to writer
	 * Hence the claim that Linux rwlocks are unfair to writers.
	 * (can be starved for an indefinite time by readers).
	 */
	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
		rw->counter = 0;
		ret = 1;
	}
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);

	return ret;
}

static inline void arch_read_lock(arch_rwlock_t *rw)
{
	while (!arch_read_trylock(rw))
		cpu_relax();
}

static inline void arch_write_lock(arch_rwlock_t *rw)
{
	while (!arch_write_trylock(rw))
		cpu_relax();
}

static inline void arch_read_unlock(arch_rwlock_t *rw)
{
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));
	rw->counter++;
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);
}

static inline void arch_write_unlock(arch_rwlock_t *rw)
{
	unsigned long flags;

	local_irq_save(flags);
	arch_spin_lock(&(rw->lock_mutex));
	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
	arch_spin_unlock(&(rw->lock_mutex));
	local_irq_restore(flags);
}

#endif

#define arch_read_lock_flags(lock, flags)	arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags)	arch_write_lock(lock)

#define arch_spin_relax(lock)	cpu_relax()
#define arch_read_relax(lock)	cpu_relax()
#define arch_write_relax(lock)	cpu_relax()

#endif /* __ASM_SPINLOCK_H */