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#ifndef __s390x__
 47#define RWSEM_UNLOCKED_VALUE	0x00000000
 48#define RWSEM_ACTIVE_BIAS	0x00000001
 49#define RWSEM_ACTIVE_MASK	0x0000ffff
 50#define RWSEM_WAITING_BIAS	(-0x00010000)
 51#else /* __s390x__ */
 52#define RWSEM_UNLOCKED_VALUE	0x0000000000000000L
 53#define RWSEM_ACTIVE_BIAS	0x0000000000000001L
 54#define RWSEM_ACTIVE_MASK	0x00000000ffffffffL
 55#define RWSEM_WAITING_BIAS	(-0x0000000100000000L)
 56#endif /* __s390x__ */
 57#define RWSEM_ACTIVE_READ_BIAS	RWSEM_ACTIVE_BIAS
 58#define RWSEM_ACTIVE_WRITE_BIAS	(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
 59
 60/*
 61 * lock for reading
 62 */
 63static inline void __down_read(struct rw_semaphore *sem)
 64{
 65	signed long old, new;
 66
 67	asm volatile(
 68#ifndef __s390x__
 69		"	l	%0,%2\n"
 70		"0:	lr	%1,%0\n"
 71		"	ahi	%1,%4\n"
 72		"	cs	%0,%1,%2\n"
 73		"	jl	0b"
 74#else /* __s390x__ */
 75		"	lg	%0,%2\n"
 76		"0:	lgr	%1,%0\n"
 77		"	aghi	%1,%4\n"
 78		"	csg	%0,%1,%2\n"
 79		"	jl	0b"
 80#endif /* __s390x__ */
 81		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
 82		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
 83		: "cc", "memory");
 84	if (old < 0)
 85		rwsem_down_read_failed(sem);
 86}
 87
 88/*
 89 * trylock for reading -- returns 1 if successful, 0 if contention
 90 */
 91static inline int __down_read_trylock(struct rw_semaphore *sem)
 92{
 93	signed long old, new;
 94
 95	asm volatile(
 96#ifndef __s390x__
 97		"	l	%0,%2\n"
 98		"0:	ltr	%1,%0\n"
 99		"	jm	1f\n"
100		"	ahi	%1,%4\n"
101		"	cs	%0,%1,%2\n"
102		"	jl	0b\n"
103		"1:"
104#else /* __s390x__ */
105		"	lg	%0,%2\n"
106		"0:	ltgr	%1,%0\n"
107		"	jm	1f\n"
108		"	aghi	%1,%4\n"
109		"	csg	%0,%1,%2\n"
110		"	jl	0b\n"
111		"1:"
112#endif /* __s390x__ */
113		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
114		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
115		: "cc", "memory");
116	return old >= 0 ? 1 : 0;
117}
118
119/*
120 * lock for writing
121 */
122static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
123{
124	signed long old, new, tmp;
125
126	tmp = RWSEM_ACTIVE_WRITE_BIAS;
127	asm volatile(
128#ifndef __s390x__
129		"	l	%0,%2\n"
130		"0:	lr	%1,%0\n"
131		"	a	%1,%4\n"
132		"	cs	%0,%1,%2\n"
133		"	jl	0b"
134#else /* __s390x__ */
135		"	lg	%0,%2\n"
136		"0:	lgr	%1,%0\n"
137		"	ag	%1,%4\n"
138		"	csg	%0,%1,%2\n"
139		"	jl	0b"
140#endif /* __s390x__ */
141		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
142		: "Q" (sem->count), "m" (tmp)
143		: "cc", "memory");
144	if (old != 0)
145		rwsem_down_write_failed(sem);
146}
147
148static inline void __down_write(struct rw_semaphore *sem)
149{
150	__down_write_nested(sem, 0);
151}
152
153/*
154 * trylock for writing -- returns 1 if successful, 0 if contention
155 */
156static inline int __down_write_trylock(struct rw_semaphore *sem)
157{
158	signed long old;
159
160	asm volatile(
161#ifndef __s390x__
162		"	l	%0,%1\n"
163		"0:	ltr	%0,%0\n"
164		"	jnz	1f\n"
165		"	cs	%0,%3,%1\n"
166		"	jl	0b\n"
167#else /* __s390x__ */
168		"	lg	%0,%1\n"
169		"0:	ltgr	%0,%0\n"
170		"	jnz	1f\n"
171		"	csg	%0,%3,%1\n"
172		"	jl	0b\n"
173#endif /* __s390x__ */
174		"1:"
175		: "=&d" (old), "=Q" (sem->count)
176		: "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)
177		: "cc", "memory");
178	return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
179}
180
181/*
182 * unlock after reading
183 */
184static inline void __up_read(struct rw_semaphore *sem)
185{
186	signed long old, new;
187
188	asm volatile(
189#ifndef __s390x__
190		"	l	%0,%2\n"
191		"0:	lr	%1,%0\n"
192		"	ahi	%1,%4\n"
193		"	cs	%0,%1,%2\n"
194		"	jl	0b"
195#else /* __s390x__ */
196		"	lg	%0,%2\n"
197		"0:	lgr	%1,%0\n"
198		"	aghi	%1,%4\n"
199		"	csg	%0,%1,%2\n"
200		"	jl	0b"
201#endif /* __s390x__ */
202		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
203		: "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)
204		: "cc", "memory");
205	if (new < 0)
206		if ((new & RWSEM_ACTIVE_MASK) == 0)
207			rwsem_wake(sem);
208}
209
210/*
211 * unlock after writing
212 */
213static inline void __up_write(struct rw_semaphore *sem)
214{
215	signed long old, new, tmp;
216
217	tmp = -RWSEM_ACTIVE_WRITE_BIAS;
218	asm volatile(
219#ifndef __s390x__
220		"	l	%0,%2\n"
221		"0:	lr	%1,%0\n"
222		"	a	%1,%4\n"
223		"	cs	%0,%1,%2\n"
224		"	jl	0b"
225#else /* __s390x__ */
226		"	lg	%0,%2\n"
227		"0:	lgr	%1,%0\n"
228		"	ag	%1,%4\n"
229		"	csg	%0,%1,%2\n"
230		"	jl	0b"
231#endif /* __s390x__ */
232		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
233		: "Q" (sem->count), "m" (tmp)
234		: "cc", "memory");
235	if (new < 0)
236		if ((new & RWSEM_ACTIVE_MASK) == 0)
237			rwsem_wake(sem);
238}
239
240/*
241 * downgrade write lock to read lock
242 */
243static inline void __downgrade_write(struct rw_semaphore *sem)
244{
245	signed long old, new, tmp;
246
247	tmp = -RWSEM_WAITING_BIAS;
248	asm volatile(
249#ifndef __s390x__
250		"	l	%0,%2\n"
251		"0:	lr	%1,%0\n"
252		"	a	%1,%4\n"
253		"	cs	%0,%1,%2\n"
254		"	jl	0b"
255#else /* __s390x__ */
256		"	lg	%0,%2\n"
257		"0:	lgr	%1,%0\n"
258		"	ag	%1,%4\n"
259		"	csg	%0,%1,%2\n"
260		"	jl	0b"
261#endif /* __s390x__ */
262		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
263		: "Q" (sem->count), "m" (tmp)
264		: "cc", "memory");
265	if (new > 1)
266		rwsem_downgrade_wake(sem);
267}
268
269/*
270 * implement atomic add functionality
271 */
272static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
273{
274	signed long old, new;
275
276	asm volatile(
277#ifndef __s390x__
278		"	l	%0,%2\n"
279		"0:	lr	%1,%0\n"
280		"	ar	%1,%4\n"
281		"	cs	%0,%1,%2\n"
282		"	jl	0b"
283#else /* __s390x__ */
284		"	lg	%0,%2\n"
285		"0:	lgr	%1,%0\n"
286		"	agr	%1,%4\n"
287		"	csg	%0,%1,%2\n"
288		"	jl	0b"
289#endif /* __s390x__ */
290		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
291		: "Q" (sem->count), "d" (delta)
292		: "cc", "memory");
293}
294
295/*
296 * implement exchange and add functionality
297 */
298static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
299{
300	signed long old, new;
301
302	asm volatile(
303#ifndef __s390x__
304		"	l	%0,%2\n"
305		"0:	lr	%1,%0\n"
306		"	ar	%1,%4\n"
307		"	cs	%0,%1,%2\n"
308		"	jl	0b"
309#else /* __s390x__ */
310		"	lg	%0,%2\n"
311		"0:	lgr	%1,%0\n"
312		"	agr	%1,%4\n"
313		"	csg	%0,%1,%2\n"
314		"	jl	0b"
315#endif /* __s390x__ */
316		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
317		: "Q" (sem->count), "d" (delta)
318		: "cc", "memory");
319	return new;
320}
321
322#endif /* __KERNEL__ */
323#endif /* _S390_RWSEM_H */