Merge tag 'pm+acpi-4.2-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael...
[linux/fpc-iii.git] / arch / s390 / include / asm / rwsem.h
blob4b43ee7e6776ca0ff98c2c2317cd4d25167b8409
1 #ifndef _S390_RWSEM_H
2 #define _S390_RWSEM_H
4 /*
5 * S390 version
6 * Copyright IBM Corp. 2002
7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
9 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
14 * The MSW of the count is the negated number of active writers and waiting
15 * lockers, and the LSW is the total number of active locks
17 * The lock count is initialized to 0 (no active and no waiting lockers).
19 * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
20 * uncontended lock. This can be determined because XADD returns the old value.
21 * Readers increment by 1 and see a positive value when uncontended, negative
22 * if there are writers (and maybe) readers waiting (in which case it goes to
23 * sleep).
25 * The value of WAITING_BIAS supports up to 32766 waiting processes. This can
26 * be extended to 65534 by manually checking the whole MSW rather than relying
27 * on the S flag.
29 * The value of ACTIVE_BIAS supports up to 65535 active processes.
31 * This should be totally fair - if anything is waiting, a process that wants a
32 * lock will go to the back of the queue. When the currently active lock is
33 * released, if there's a writer at the front of the queue, then that and only
34 * that will be woken up; if there's a bunch of consequtive readers at the
35 * front, then they'll all be woken up, but no other readers will be.
38 #ifndef _LINUX_RWSEM_H
39 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
40 #endif
42 #define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
43 #define RWSEM_ACTIVE_BIAS 0x0000000000000001L
44 #define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
45 #define RWSEM_WAITING_BIAS (-0x0000000100000000L)
46 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
47 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
50 * lock for reading
52 static inline void __down_read(struct rw_semaphore *sem)
54 signed long old, new;
56 asm volatile(
57 " lg %0,%2\n"
58 "0: lgr %1,%0\n"
59 " aghi %1,%4\n"
60 " csg %0,%1,%2\n"
61 " jl 0b"
62 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
63 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
64 : "cc", "memory");
65 if (old < 0)
66 rwsem_down_read_failed(sem);
70 * trylock for reading -- returns 1 if successful, 0 if contention
72 static inline int __down_read_trylock(struct rw_semaphore *sem)
74 signed long old, new;
76 asm volatile(
77 " lg %0,%2\n"
78 "0: ltgr %1,%0\n"
79 " jm 1f\n"
80 " aghi %1,%4\n"
81 " csg %0,%1,%2\n"
82 " jl 0b\n"
83 "1:"
84 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
85 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
86 : "cc", "memory");
87 return old >= 0 ? 1 : 0;
91 * lock for writing
93 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
95 signed long old, new, tmp;
97 tmp = RWSEM_ACTIVE_WRITE_BIAS;
98 asm volatile(
99 " lg %0,%2\n"
100 "0: lgr %1,%0\n"
101 " ag %1,%4\n"
102 " csg %0,%1,%2\n"
103 " jl 0b"
104 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
105 : "Q" (sem->count), "m" (tmp)
106 : "cc", "memory");
107 if (old != 0)
108 rwsem_down_write_failed(sem);
111 static inline void __down_write(struct rw_semaphore *sem)
113 __down_write_nested(sem, 0);
117 * trylock for writing -- returns 1 if successful, 0 if contention
119 static inline int __down_write_trylock(struct rw_semaphore *sem)
121 signed long old;
123 asm volatile(
124 " lg %0,%1\n"
125 "0: ltgr %0,%0\n"
126 " jnz 1f\n"
127 " csg %0,%3,%1\n"
128 " jl 0b\n"
129 "1:"
130 : "=&d" (old), "=Q" (sem->count)
131 : "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)
132 : "cc", "memory");
133 return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
137 * unlock after reading
139 static inline void __up_read(struct rw_semaphore *sem)
141 signed long old, new;
143 asm volatile(
144 " lg %0,%2\n"
145 "0: lgr %1,%0\n"
146 " aghi %1,%4\n"
147 " csg %0,%1,%2\n"
148 " jl 0b"
149 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
150 : "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)
151 : "cc", "memory");
152 if (new < 0)
153 if ((new & RWSEM_ACTIVE_MASK) == 0)
154 rwsem_wake(sem);
158 * unlock after writing
160 static inline void __up_write(struct rw_semaphore *sem)
162 signed long old, new, tmp;
164 tmp = -RWSEM_ACTIVE_WRITE_BIAS;
165 asm volatile(
166 " lg %0,%2\n"
167 "0: lgr %1,%0\n"
168 " ag %1,%4\n"
169 " csg %0,%1,%2\n"
170 " jl 0b"
171 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
172 : "Q" (sem->count), "m" (tmp)
173 : "cc", "memory");
174 if (new < 0)
175 if ((new & RWSEM_ACTIVE_MASK) == 0)
176 rwsem_wake(sem);
180 * downgrade write lock to read lock
182 static inline void __downgrade_write(struct rw_semaphore *sem)
184 signed long old, new, tmp;
186 tmp = -RWSEM_WAITING_BIAS;
187 asm volatile(
188 " lg %0,%2\n"
189 "0: lgr %1,%0\n"
190 " ag %1,%4\n"
191 " csg %0,%1,%2\n"
192 " jl 0b"
193 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
194 : "Q" (sem->count), "m" (tmp)
195 : "cc", "memory");
196 if (new > 1)
197 rwsem_downgrade_wake(sem);
201 * implement atomic add functionality
203 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
205 signed long old, new;
207 asm volatile(
208 " lg %0,%2\n"
209 "0: lgr %1,%0\n"
210 " agr %1,%4\n"
211 " csg %0,%1,%2\n"
212 " jl 0b"
213 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
214 : "Q" (sem->count), "d" (delta)
215 : "cc", "memory");
219 * implement exchange and add functionality
221 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
223 signed long old, new;
225 asm volatile(
226 " lg %0,%2\n"
227 "0: lgr %1,%0\n"
228 " agr %1,%4\n"
229 " csg %0,%1,%2\n"
230 " jl 0b"
231 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
232 : "Q" (sem->count), "d" (delta)
233 : "cc", "memory");
234 return new;
237 #endif /* _S390_RWSEM_H */