1 /*
2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 #ifndef __ASM_SPINLOCK_H
10 #define __ASM_SPINLOCK_H
11
12 #include <asm/spinlock_types.h>
13 #include <asm/processor.h>
14 #include <asm/barrier.h>
15
16 #define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
17 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
18
arch_spin_unlock_wait(arch_spinlock_t * lock)19 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
20 {
21 smp_cond_load_acquire(&lock->slock, !VAL);
22 }
23
24 #ifdef CONFIG_ARC_HAS_LLSC
25
arch_spin_lock(arch_spinlock_t * lock)26 static inline void arch_spin_lock(arch_spinlock_t *lock)
27 {
28 unsigned int val;
29
30 smp_mb();
31
32 __asm__ __volatile__(
33 "1: llock %[val], [%[slock]] \n"
34 " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */
35 " scond %[LOCKED], [%[slock]] \n" /* acquire */
36 " bnz 1b \n"
37 " \n"
38 : [val] "=&r" (val)
39 : [slock] "r" (&(lock->slock)),
40 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
41 : "memory", "cc");
42
43 smp_mb();
44 }
45
46 /* 1 - lock taken successfully */
arch_spin_trylock(arch_spinlock_t * lock)47 static inline int arch_spin_trylock(arch_spinlock_t *lock)
48 {
49 unsigned int val, got_it = 0;
50
51 smp_mb();
52
53 __asm__ __volatile__(
54 "1: llock %[val], [%[slock]] \n"
55 " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
56 " scond %[LOCKED], [%[slock]] \n" /* acquire */
57 " bnz 1b \n"
58 " mov %[got_it], 1 \n"
59 "4: \n"
60 " \n"
61 : [val] "=&r" (val),
62 [got_it] "+&r" (got_it)
63 : [slock] "r" (&(lock->slock)),
64 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
65 : "memory", "cc");
66
67 smp_mb();
68
69 return got_it;
70 }
71
arch_spin_unlock(arch_spinlock_t * lock)72 static inline void arch_spin_unlock(arch_spinlock_t *lock)
73 {
74 smp_mb();
75
76 lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
77
78 smp_mb();
79 }
80
81 /*
82 * Read-write spinlocks, allowing multiple readers but only one writer.
83 * Unfair locking as Writers could be starved indefinitely by Reader(s)
84 */
85
arch_read_lock(arch_rwlock_t * rw)86 static inline void arch_read_lock(arch_rwlock_t *rw)
87 {
88 unsigned int val;
89
90 smp_mb();
91
92 /*
93 * zero means writer holds the lock exclusively, deny Reader.
94 * Otherwise grant lock to first/subseq reader
95 *
96 * if (rw->counter > 0) {
97 * rw->counter--;
98 * ret = 1;
99 * }
100 */
101
102 __asm__ __volatile__(
103 "1: llock %[val], [%[rwlock]] \n"
104 " brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */
105 " sub %[val], %[val], 1 \n" /* reader lock */
106 " scond %[val], [%[rwlock]] \n"
107 " bnz 1b \n"
108 " \n"
109 : [val] "=&r" (val)
110 : [rwlock] "r" (&(rw->counter)),
111 [WR_LOCKED] "ir" (0)
112 : "memory", "cc");
113
114 smp_mb();
115 }
116
117 /* 1 - lock taken successfully */
arch_read_trylock(arch_rwlock_t * rw)118 static inline int arch_read_trylock(arch_rwlock_t *rw)
119 {
120 unsigned int val, got_it = 0;
121
122 smp_mb();
123
124 __asm__ __volatile__(
125 "1: llock %[val], [%[rwlock]] \n"
126 " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
127 " sub %[val], %[val], 1 \n" /* counter-- */
128 " scond %[val], [%[rwlock]] \n"
129 " bnz 1b \n" /* retry if collided with someone */
130 " mov %[got_it], 1 \n"
131 " \n"
132 "4: ; --- done --- \n"
133
134 : [val] "=&r" (val),
135 [got_it] "+&r" (got_it)
136 : [rwlock] "r" (&(rw->counter)),
137 [WR_LOCKED] "ir" (0)
138 : "memory", "cc");
139
140 smp_mb();
141
142 return got_it;
143 }
144
arch_write_lock(arch_rwlock_t * rw)145 static inline void arch_write_lock(arch_rwlock_t *rw)
146 {
147 unsigned int val;
148
149 smp_mb();
150
151 /*
152 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
153 * deny writer. Otherwise if unlocked grant to writer
154 * Hence the claim that Linux rwlocks are unfair to writers.
155 * (can be starved for an indefinite time by readers).
156 *
157 * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
158 * rw->counter = 0;
159 * ret = 1;
160 * }
161 */
162
163 __asm__ __volatile__(
164 "1: llock %[val], [%[rwlock]] \n"
165 " brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */
166 " mov %[val], %[WR_LOCKED] \n"
167 " scond %[val], [%[rwlock]] \n"
168 " bnz 1b \n"
169 " \n"
170 : [val] "=&r" (val)
171 : [rwlock] "r" (&(rw->counter)),
172 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
173 [WR_LOCKED] "ir" (0)
174 : "memory", "cc");
175
176 smp_mb();
177 }
178
179 /* 1 - lock taken successfully */
arch_write_trylock(arch_rwlock_t * rw)180 static inline int arch_write_trylock(arch_rwlock_t *rw)
181 {
182 unsigned int val, got_it = 0;
183
184 smp_mb();
185
186 __asm__ __volatile__(
187 "1: llock %[val], [%[rwlock]] \n"
188 " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
189 " mov %[val], %[WR_LOCKED] \n"
190 " scond %[val], [%[rwlock]] \n"
191 " bnz 1b \n" /* retry if collided with someone */
192 " mov %[got_it], 1 \n"
193 " \n"
194 "4: ; --- done --- \n"
195
196 : [val] "=&r" (val),
197 [got_it] "+&r" (got_it)
198 : [rwlock] "r" (&(rw->counter)),
199 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
200 [WR_LOCKED] "ir" (0)
201 : "memory", "cc");
202
203 smp_mb();
204
205 return got_it;
206 }
207
arch_read_unlock(arch_rwlock_t * rw)208 static inline void arch_read_unlock(arch_rwlock_t *rw)
209 {
210 unsigned int val;
211
212 smp_mb();
213
214 /*
215 * rw->counter++;
216 */
217 __asm__ __volatile__(
218 "1: llock %[val], [%[rwlock]] \n"
219 " add %[val], %[val], 1 \n"
220 " scond %[val], [%[rwlock]] \n"
221 " bnz 1b \n"
222 " \n"
223 : [val] "=&r" (val)
224 : [rwlock] "r" (&(rw->counter))
225 : "memory", "cc");
226
227 smp_mb();
228 }
229
arch_write_unlock(arch_rwlock_t * rw)230 static inline void arch_write_unlock(arch_rwlock_t *rw)
231 {
232 smp_mb();
233
234 rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
235
236 smp_mb();
237 }
238
239 #else /* !CONFIG_ARC_HAS_LLSC */
240
arch_spin_lock(arch_spinlock_t * lock)241 static inline void arch_spin_lock(arch_spinlock_t *lock)
242 {
243 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
244
245 /*
246 * This smp_mb() is technically superfluous, we only need the one
247 * after the lock for providing the ACQUIRE semantics.
248 * However doing the "right" thing was regressing hackbench
249 * so keeping this, pending further investigation
250 */
251 smp_mb();
252
253 __asm__ __volatile__(
254 "1: ex %0, [%1] \n"
255 " breq %0, %2, 1b \n"
256 : "+&r" (val)
257 : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
258 : "memory");
259
260 /*
261 * ACQUIRE barrier to ensure load/store after taking the lock
262 * don't "bleed-up" out of the critical section (leak-in is allowed)
263 * http://www.spinics.net/lists/kernel/msg2010409.html
264 *
265 * ARCv2 only has load-load, store-store and all-all barrier
266 * thus need the full all-all barrier
267 */
268 smp_mb();
269 }
270
271 /* 1 - lock taken successfully */
arch_spin_trylock(arch_spinlock_t * lock)272 static inline int arch_spin_trylock(arch_spinlock_t *lock)
273 {
274 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
275
276 smp_mb();
277
278 __asm__ __volatile__(
279 "1: ex %0, [%1] \n"
280 : "+r" (val)
281 : "r"(&(lock->slock))
282 : "memory");
283
284 smp_mb();
285
286 return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
287 }
288
arch_spin_unlock(arch_spinlock_t * lock)289 static inline void arch_spin_unlock(arch_spinlock_t *lock)
290 {
291 unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;
292
293 /*
294 * RELEASE barrier: given the instructions avail on ARCv2, full barrier
295 * is the only option
296 */
297 smp_mb();
298
299 __asm__ __volatile__(
300 " ex %0, [%1] \n"
301 : "+r" (val)
302 : "r"(&(lock->slock))
303 : "memory");
304
305 /*
306 * superfluous, but keeping for now - see pairing version in
307 * arch_spin_lock above
308 */
309 smp_mb();
310 }
311
312 /*
313 * Read-write spinlocks, allowing multiple readers but only one writer.
314 * Unfair locking as Writers could be starved indefinitely by Reader(s)
315 *
316 * The spinlock itself is contained in @counter and access to it is
317 * serialized with @lock_mutex.
318 */
319
320 /* 1 - lock taken successfully */
arch_read_trylock(arch_rwlock_t * rw)321 static inline int arch_read_trylock(arch_rwlock_t *rw)
322 {
323 int ret = 0;
324 unsigned long flags;
325
326 local_irq_save(flags);
327 arch_spin_lock(&(rw->lock_mutex));
328
329 /*
330 * zero means writer holds the lock exclusively, deny Reader.
331 * Otherwise grant lock to first/subseq reader
332 */
333 if (rw->counter > 0) {
334 rw->counter--;
335 ret = 1;
336 }
337
338 arch_spin_unlock(&(rw->lock_mutex));
339 local_irq_restore(flags);
340
341 smp_mb();
342 return ret;
343 }
344
345 /* 1 - lock taken successfully */
arch_write_trylock(arch_rwlock_t * rw)346 static inline int arch_write_trylock(arch_rwlock_t *rw)
347 {
348 int ret = 0;
349 unsigned long flags;
350
351 local_irq_save(flags);
352 arch_spin_lock(&(rw->lock_mutex));
353
354 /*
355 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
356 * deny writer. Otherwise if unlocked grant to writer
357 * Hence the claim that Linux rwlocks are unfair to writers.
358 * (can be starved for an indefinite time by readers).
359 */
360 if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
361 rw->counter = 0;
362 ret = 1;
363 }
364 arch_spin_unlock(&(rw->lock_mutex));
365 local_irq_restore(flags);
366
367 return ret;
368 }
369
arch_read_lock(arch_rwlock_t * rw)370 static inline void arch_read_lock(arch_rwlock_t *rw)
371 {
372 while (!arch_read_trylock(rw))
373 cpu_relax();
374 }
375
arch_write_lock(arch_rwlock_t * rw)376 static inline void arch_write_lock(arch_rwlock_t *rw)
377 {
378 while (!arch_write_trylock(rw))
379 cpu_relax();
380 }
381
arch_read_unlock(arch_rwlock_t * rw)382 static inline void arch_read_unlock(arch_rwlock_t *rw)
383 {
384 unsigned long flags;
385
386 local_irq_save(flags);
387 arch_spin_lock(&(rw->lock_mutex));
388 rw->counter++;
389 arch_spin_unlock(&(rw->lock_mutex));
390 local_irq_restore(flags);
391 }
392
arch_write_unlock(arch_rwlock_t * rw)393 static inline void arch_write_unlock(arch_rwlock_t *rw)
394 {
395 unsigned long flags;
396
397 local_irq_save(flags);
398 arch_spin_lock(&(rw->lock_mutex));
399 rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
400 arch_spin_unlock(&(rw->lock_mutex));
401 local_irq_restore(flags);
402 }
403
404 #endif
405
406 #define arch_read_can_lock(x) ((x)->counter > 0)
407 #define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
408
409 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
410 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
411
412 #define arch_spin_relax(lock) cpu_relax()
413 #define arch_read_relax(lock) cpu_relax()
414 #define arch_write_relax(lock) cpu_relax()
415
416 #endif /* __ASM_SPINLOCK_H */
417