1 #ifndef _S390_RWSEM_H
2 #define _S390_RWSEM_H
3
4 /*
5 * include/asm-s390/rwsem.h
6 *
7 * S390 version
8 * Copyright (C) 2002 IBM Deutschland Entwicklung GmbH, IBM Corporation
9 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
10 *
11 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
12 */
13
14 /*
15 *
16 * The MSW of the count is the negated number of active writers and waiting
17 * lockers, and the LSW is the total number of active locks
18 *
19 * The lock count is initialized to 0 (no active and no waiting lockers).
20 *
21 * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
22 * uncontended lock. This can be determined because XADD returns the old value.
23 * Readers increment by 1 and see a positive value when uncontended, negative
24 * if there are writers (and maybe) readers waiting (in which case it goes to
25 * sleep).
26 *
27 * The value of WAITING_BIAS supports up to 32766 waiting processes. This can
28 * be extended to 65534 by manually checking the whole MSW rather than relying
29 * on the S flag.
30 *
31 * The value of ACTIVE_BIAS supports up to 65535 active processes.
32 *
33 * This should be totally fair - if anything is waiting, a process that wants a
34 * lock will go to the back of the queue. When the currently active lock is
35 * released, if there's a writer at the front of the queue, then that and only
36 * that will be woken up; if there's a bunch of consequtive readers at the
37 * front, then they'll all be woken up, but no other readers will be.
38 */
39
40 #ifndef _LINUX_RWSEM_H
41 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
42 #endif
43
44 #ifdef __KERNEL__
45
46 #include <linux/list.h>
47 #include <linux/spinlock.h>
48
49 struct rwsem_waiter;
50
51 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *);
52 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *);
53 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
54 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *);
55 extern struct rw_semaphore *rwsem_downgrade_write(struct rw_semaphore *);
56
57 /*
58 * the semaphore definition
59 */
60 struct rw_semaphore {
61 signed long count;
62 spinlock_t wait_lock;
63 struct list_head wait_list;
64 #ifdef CONFIG_DEBUG_LOCK_ALLOC
65 struct lockdep_map dep_map;
66 #endif
67 };
68
69 #ifndef __s390x__
70 #define RWSEM_UNLOCKED_VALUE 0x00000000
71 #define RWSEM_ACTIVE_BIAS 0x00000001
72 #define RWSEM_ACTIVE_MASK 0x0000ffff
73 #define RWSEM_WAITING_BIAS (-0x00010000)
74 #else /* __s390x__ */
75 #define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
76 #define RWSEM_ACTIVE_BIAS 0x0000000000000001L
77 #define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
78 #define RWSEM_WAITING_BIAS (-0x0000000100000000L)
79 #endif /* __s390x__ */
80 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
81 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
82
83 /*
84 * initialisation
85 */
86
87 #ifdef CONFIG_DEBUG_LOCK_ALLOC
88 # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
89 #else
90 # define __RWSEM_DEP_MAP_INIT(lockname)
91 #endif
92
93 #define __RWSEM_INITIALIZER(name) \
94 { RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait.lock), \
95 LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
96
97 #define DECLARE_RWSEM(name) \
98 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
99
init_rwsem(struct rw_semaphore * sem)100 static inline void init_rwsem(struct rw_semaphore *sem)
101 {
102 sem->count = RWSEM_UNLOCKED_VALUE;
103 spin_lock_init(&sem->wait_lock);
104 INIT_LIST_HEAD(&sem->wait_list);
105 }
106
107 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
108 struct lock_class_key *key);
109
110 #define init_rwsem(sem) \
111 do { \
112 static struct lock_class_key __key; \
113 \
114 __init_rwsem((sem), #sem, &__key); \
115 } while (0)
116
117
118 /*
119 * lock for reading
120 */
__down_read(struct rw_semaphore * sem)121 static inline void __down_read(struct rw_semaphore *sem)
122 {
123 signed long old, new;
124
125 asm volatile(
126 #ifndef __s390x__
127 " l %0,0(%3)\n"
128 "0: lr %1,%0\n"
129 " ahi %1,%5\n"
130 " cs %0,%1,0(%3)\n"
131 " jl 0b"
132 #else /* __s390x__ */
133 " lg %0,0(%3)\n"
134 "0: lgr %1,%0\n"
135 " aghi %1,%5\n"
136 " csg %0,%1,0(%3)\n"
137 " jl 0b"
138 #endif /* __s390x__ */
139 : "=&d" (old), "=&d" (new), "=m" (sem->count)
140 : "a" (&sem->count), "m" (sem->count),
141 "i" (RWSEM_ACTIVE_READ_BIAS) : "cc", "memory");
142 if (old < 0)
143 rwsem_down_read_failed(sem);
144 }
145
146 /*
147 * trylock for reading -- returns 1 if successful, 0 if contention
148 */
__down_read_trylock(struct rw_semaphore * sem)149 static inline int __down_read_trylock(struct rw_semaphore *sem)
150 {
151 signed long old, new;
152
153 asm volatile(
154 #ifndef __s390x__
155 " l %0,0(%3)\n"
156 "0: ltr %1,%0\n"
157 " jm 1f\n"
158 " ahi %1,%5\n"
159 " cs %0,%1,0(%3)\n"
160 " jl 0b\n"
161 "1:"
162 #else /* __s390x__ */
163 " lg %0,0(%3)\n"
164 "0: ltgr %1,%0\n"
165 " jm 1f\n"
166 " aghi %1,%5\n"
167 " csg %0,%1,0(%3)\n"
168 " jl 0b\n"
169 "1:"
170 #endif /* __s390x__ */
171 : "=&d" (old), "=&d" (new), "=m" (sem->count)
172 : "a" (&sem->count), "m" (sem->count),
173 "i" (RWSEM_ACTIVE_READ_BIAS) : "cc", "memory");
174 return old >= 0 ? 1 : 0;
175 }
176
177 /*
178 * lock for writing
179 */
__down_write_nested(struct rw_semaphore * sem,int subclass)180 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
181 {
182 signed long old, new, tmp;
183
184 tmp = RWSEM_ACTIVE_WRITE_BIAS;
185 asm volatile(
186 #ifndef __s390x__
187 " l %0,0(%3)\n"
188 "0: lr %1,%0\n"
189 " a %1,%5\n"
190 " cs %0,%1,0(%3)\n"
191 " jl 0b"
192 #else /* __s390x__ */
193 " lg %0,0(%3)\n"
194 "0: lgr %1,%0\n"
195 " ag %1,%5\n"
196 " csg %0,%1,0(%3)\n"
197 " jl 0b"
198 #endif /* __s390x__ */
199 : "=&d" (old), "=&d" (new), "=m" (sem->count)
200 : "a" (&sem->count), "m" (sem->count), "m" (tmp)
201 : "cc", "memory");
202 if (old != 0)
203 rwsem_down_write_failed(sem);
204 }
205
__down_write(struct rw_semaphore * sem)206 static inline void __down_write(struct rw_semaphore *sem)
207 {
208 __down_write_nested(sem, 0);
209 }
210
211 /*
212 * trylock for writing -- returns 1 if successful, 0 if contention
213 */
__down_write_trylock(struct rw_semaphore * sem)214 static inline int __down_write_trylock(struct rw_semaphore *sem)
215 {
216 signed long old;
217
218 asm volatile(
219 #ifndef __s390x__
220 " l %0,0(%2)\n"
221 "0: ltr %0,%0\n"
222 " jnz 1f\n"
223 " cs %0,%4,0(%2)\n"
224 " jl 0b\n"
225 #else /* __s390x__ */
226 " lg %0,0(%2)\n"
227 "0: ltgr %0,%0\n"
228 " jnz 1f\n"
229 " csg %0,%4,0(%2)\n"
230 " jl 0b\n"
231 #endif /* __s390x__ */
232 "1:"
233 : "=&d" (old), "=m" (sem->count)
234 : "a" (&sem->count), "m" (sem->count),
235 "d" (RWSEM_ACTIVE_WRITE_BIAS) : "cc", "memory");
236 return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
237 }
238
239 /*
240 * unlock after reading
241 */
__up_read(struct rw_semaphore * sem)242 static inline void __up_read(struct rw_semaphore *sem)
243 {
244 signed long old, new;
245
246 asm volatile(
247 #ifndef __s390x__
248 " l %0,0(%3)\n"
249 "0: lr %1,%0\n"
250 " ahi %1,%5\n"
251 " cs %0,%1,0(%3)\n"
252 " jl 0b"
253 #else /* __s390x__ */
254 " lg %0,0(%3)\n"
255 "0: lgr %1,%0\n"
256 " aghi %1,%5\n"
257 " csg %0,%1,0(%3)\n"
258 " jl 0b"
259 #endif /* __s390x__ */
260 : "=&d" (old), "=&d" (new), "=m" (sem->count)
261 : "a" (&sem->count), "m" (sem->count),
262 "i" (-RWSEM_ACTIVE_READ_BIAS)
263 : "cc", "memory");
264 if (new < 0)
265 if ((new & RWSEM_ACTIVE_MASK) == 0)
266 rwsem_wake(sem);
267 }
268
269 /*
270 * unlock after writing
271 */
__up_write(struct rw_semaphore * sem)272 static inline void __up_write(struct rw_semaphore *sem)
273 {
274 signed long old, new, tmp;
275
276 tmp = -RWSEM_ACTIVE_WRITE_BIAS;
277 asm volatile(
278 #ifndef __s390x__
279 " l %0,0(%3)\n"
280 "0: lr %1,%0\n"
281 " a %1,%5\n"
282 " cs %0,%1,0(%3)\n"
283 " jl 0b"
284 #else /* __s390x__ */
285 " lg %0,0(%3)\n"
286 "0: lgr %1,%0\n"
287 " ag %1,%5\n"
288 " csg %0,%1,0(%3)\n"
289 " jl 0b"
290 #endif /* __s390x__ */
291 : "=&d" (old), "=&d" (new), "=m" (sem->count)
292 : "a" (&sem->count), "m" (sem->count), "m" (tmp)
293 : "cc", "memory");
294 if (new < 0)
295 if ((new & RWSEM_ACTIVE_MASK) == 0)
296 rwsem_wake(sem);
297 }
298
299 /*
300 * downgrade write lock to read lock
301 */
__downgrade_write(struct rw_semaphore * sem)302 static inline void __downgrade_write(struct rw_semaphore *sem)
303 {
304 signed long old, new, tmp;
305
306 tmp = -RWSEM_WAITING_BIAS;
307 asm volatile(
308 #ifndef __s390x__
309 " l %0,0(%3)\n"
310 "0: lr %1,%0\n"
311 " a %1,%5\n"
312 " cs %0,%1,0(%3)\n"
313 " jl 0b"
314 #else /* __s390x__ */
315 " lg %0,0(%3)\n"
316 "0: lgr %1,%0\n"
317 " ag %1,%5\n"
318 " csg %0,%1,0(%3)\n"
319 " jl 0b"
320 #endif /* __s390x__ */
321 : "=&d" (old), "=&d" (new), "=m" (sem->count)
322 : "a" (&sem->count), "m" (sem->count), "m" (tmp)
323 : "cc", "memory");
324 if (new > 1)
325 rwsem_downgrade_wake(sem);
326 }
327
328 /*
329 * implement atomic add functionality
330 */
rwsem_atomic_add(long delta,struct rw_semaphore * sem)331 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
332 {
333 signed long old, new;
334
335 asm volatile(
336 #ifndef __s390x__
337 " l %0,0(%3)\n"
338 "0: lr %1,%0\n"
339 " ar %1,%5\n"
340 " cs %0,%1,0(%3)\n"
341 " jl 0b"
342 #else /* __s390x__ */
343 " lg %0,0(%3)\n"
344 "0: lgr %1,%0\n"
345 " agr %1,%5\n"
346 " csg %0,%1,0(%3)\n"
347 " jl 0b"
348 #endif /* __s390x__ */
349 : "=&d" (old), "=&d" (new), "=m" (sem->count)
350 : "a" (&sem->count), "m" (sem->count), "d" (delta)
351 : "cc", "memory");
352 }
353
354 /*
355 * implement exchange and add functionality
356 */
rwsem_atomic_update(long delta,struct rw_semaphore * sem)357 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
358 {
359 signed long old, new;
360
361 asm volatile(
362 #ifndef __s390x__
363 " l %0,0(%3)\n"
364 "0: lr %1,%0\n"
365 " ar %1,%5\n"
366 " cs %0,%1,0(%3)\n"
367 " jl 0b"
368 #else /* __s390x__ */
369 " lg %0,0(%3)\n"
370 "0: lgr %1,%0\n"
371 " agr %1,%5\n"
372 " csg %0,%1,0(%3)\n"
373 " jl 0b"
374 #endif /* __s390x__ */
375 : "=&d" (old), "=&d" (new), "=m" (sem->count)
376 : "a" (&sem->count), "m" (sem->count), "d" (delta)
377 : "cc", "memory");
378 return new;
379 }
380
rwsem_is_locked(struct rw_semaphore * sem)381 static inline int rwsem_is_locked(struct rw_semaphore *sem)
382 {
383 return (sem->count != 0);
384 }
385
386 #endif /* __KERNEL__ */
387 #endif /* _S390_RWSEM_H */
388