1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 #ifndef _ASM_POWERPC_SIMPLE_SPINLOCK_H
3 #define _ASM_POWERPC_SIMPLE_SPINLOCK_H
4
5 /*
6 * Simple spin lock operations.
7 *
8 * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
9 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
10 * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
11 * Rework to support virtual processors
12 *
13 * Type of int is used as a full 64b word is not necessary.
14 *
15 * (the type definitions are in asm/simple_spinlock_types.h)
16 */
17 #include <linux/irqflags.h>
18 #include <linux/kcsan-checks.h>
19 #include <asm/paravirt.h>
20 #include <asm/paca.h>
21 #include <asm/synch.h>
22 #include <asm/ppc-opcode.h>
23
24 #ifdef CONFIG_PPC64
25 /* use 0x800000yy when locked, where yy == CPU number */
26 #ifdef __BIG_ENDIAN__
27 #define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
28 #else
29 #define LOCK_TOKEN (*(u32 *)(&get_paca()->paca_index))
30 #endif
31 #else
32 #define LOCK_TOKEN 1
33 #endif
34
35 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
36 {
37 return lock.slock == 0;
38 }
39
40 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
41 {
42 return !arch_spin_value_unlocked(READ_ONCE(*lock));
43 }
44
45 /*
46 * This returns the old value in the lock, so we succeeded
47 * in getting the lock if the return value is 0.
48 */
49 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
50 {
51 unsigned long tmp, token;
52 unsigned int eh = IS_ENABLED(CONFIG_PPC64);
53
54 token = LOCK_TOKEN;
55 __asm__ __volatile__(
56 "1: lwarx %0,0,%2,%[eh]\n\
57 cmpwi 0,%0,0\n\
58 bne- 2f\n\
59 stwcx. %1,0,%2\n\
60 bne- 1b\n"
61 PPC_ACQUIRE_BARRIER
62 "2:"
63 : "=&r" (tmp)
64 : "r" (token), "r" (&lock->slock), [eh] "n" (eh)
65 : "cr0", "memory");
66
67 return tmp;
68 }
69
70 static inline int arch_spin_trylock(arch_spinlock_t *lock)
71 {
72 return __arch_spin_trylock(lock) == 0;
73 }
74
75 /*
76 * On a system with shared processors (that is, where a physical
77 * processor is multiplexed between several virtual processors),
78 * there is no point spinning on a lock if the holder of the lock
79 * isn't currently scheduled on a physical processor. Instead
80 * we detect this situation and ask the hypervisor to give the
81 * rest of our timeslice to the lock holder.
82 *
83 * So that we can tell which virtual processor is holding a lock,
84 * we put 0x80000000 | smp_processor_id() in the lock when it is
85 * held. Conveniently, we have a word in the paca that holds this
86 * value.
87 */
88
89 #if defined(CONFIG_PPC_SPLPAR)
90 /* We only yield to the hypervisor if we are in shared processor mode */
91 void splpar_spin_yield(arch_spinlock_t *lock);
92 void splpar_rw_yield(arch_rwlock_t *lock);
93 #else /* SPLPAR */
94 static inline void splpar_spin_yield(arch_spinlock_t *lock) {}
95 static inline void splpar_rw_yield(arch_rwlock_t *lock) {}
96 #endif
97
98 static inline void spin_yield(arch_spinlock_t *lock)
99 {
100 if (is_shared_processor())
101 splpar_spin_yield(lock);
102 else
103 barrier();
104 }
105
106 static inline void rw_yield(arch_rwlock_t *lock)
107 {
108 if (is_shared_processor())
109 splpar_rw_yield(lock);
110 else
111 barrier();
112 }
113
114 static inline void arch_spin_lock(arch_spinlock_t *lock)
115 {
116 while (1) {
117 if (likely(__arch_spin_trylock(lock) == 0))
118 break;
119 do {
120 HMT_low();
121 if (is_shared_processor())
122 splpar_spin_yield(lock);
123 } while (unlikely(lock->slock != 0));
124 HMT_medium();
125 }
126 }
127
128 static inline void arch_spin_unlock(arch_spinlock_t *lock)
129 {
130 kcsan_mb();
131 __asm__ __volatile__("# arch_spin_unlock\n\t"
132 PPC_RELEASE_BARRIER: : :"memory");
133 lock->slock = 0;
134 }
135
136 /*
137 * Read-write spinlocks, allowing multiple readers
138 * but only one writer.
139 *
140 * NOTE! it is quite common to have readers in interrupts
141 * but no interrupt writers. For those circumstances we
142 * can "mix" irq-safe locks - any writer needs to get a
143 * irq-safe write-lock, but readers can get non-irqsafe
144 * read-locks.
145 */
146
147 #ifdef CONFIG_PPC64
148 #define __DO_SIGN_EXTEND "extsw %0,%0\n"
149 #define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
150 #else
151 #define __DO_SIGN_EXTEND
152 #define WRLOCK_TOKEN (-1)
153 #endif
154
155 /*
156 * This returns the old value in the lock + 1,
157 * so we got a read lock if the return value is > 0.
158 */
159 static inline long __arch_read_trylock(arch_rwlock_t *rw)
160 {
161 long tmp;
162 unsigned int eh = IS_ENABLED(CONFIG_PPC64);
163
164 __asm__ __volatile__(
165 "1: lwarx %0,0,%1,%[eh]\n"
166 __DO_SIGN_EXTEND
167 " addic. %0,%0,1\n\
168 ble- 2f\n"
169 " stwcx. %0,0,%1\n\
170 bne- 1b\n"
171 PPC_ACQUIRE_BARRIER
172 "2:" : "=&r" (tmp)
173 : "r" (&rw->lock), [eh] "n" (eh)
174 : "cr0", "xer", "memory");
175
176 return tmp;
177 }
178
179 /*
180 * This returns the old value in the lock,
181 * so we got the write lock if the return value is 0.
182 */
183 static inline long __arch_write_trylock(arch_rwlock_t *rw)
184 {
185 long tmp, token;
186 unsigned int eh = IS_ENABLED(CONFIG_PPC64);
187
188 token = WRLOCK_TOKEN;
189 __asm__ __volatile__(
190 "1: lwarx %0,0,%2,%[eh]\n\
191 cmpwi 0,%0,0\n\
192 bne- 2f\n"
193 " stwcx. %1,0,%2\n\
194 bne- 1b\n"
195 PPC_ACQUIRE_BARRIER
196 "2:" : "=&r" (tmp)
197 : "r" (token), "r" (&rw->lock), [eh] "n" (eh)
198 : "cr0", "memory");
199
200 return tmp;
201 }
202
203 static inline void arch_read_lock(arch_rwlock_t *rw)
204 {
205 while (1) {
206 if (likely(__arch_read_trylock(rw) > 0))
207 break;
208 do {
209 HMT_low();
210 if (is_shared_processor())
211 splpar_rw_yield(rw);
212 } while (unlikely(rw->lock < 0));
213 HMT_medium();
214 }
215 }
216
217 static inline void arch_write_lock(arch_rwlock_t *rw)
218 {
219 while (1) {
220 if (likely(__arch_write_trylock(rw) == 0))
221 break;
222 do {
223 HMT_low();
224 if (is_shared_processor())
225 splpar_rw_yield(rw);
226 } while (unlikely(rw->lock != 0));
227 HMT_medium();
228 }
229 }
230
231 static inline int arch_read_trylock(arch_rwlock_t *rw)
232 {
233 return __arch_read_trylock(rw) > 0;
234 }
235
236 static inline int arch_write_trylock(arch_rwlock_t *rw)
237 {
238 return __arch_write_trylock(rw) == 0;
239 }
240
241 static inline void arch_read_unlock(arch_rwlock_t *rw)
242 {
243 long tmp;
244
245 __asm__ __volatile__(
246 "# read_unlock\n\t"
247 PPC_RELEASE_BARRIER
248 "1: lwarx %0,0,%1\n\
249 addic %0,%0,-1\n"
250 " stwcx. %0,0,%1\n\
251 bne- 1b"
252 : "=&r"(tmp)
253 : "r"(&rw->lock)
254 : "cr0", "xer", "memory");
255 }
256
257 static inline void arch_write_unlock(arch_rwlock_t *rw)
258 {
259 __asm__ __volatile__("# write_unlock\n\t"
260 PPC_RELEASE_BARRIER: : :"memory");
261 rw->lock = 0;
262 }
263
264 #define arch_spin_relax(lock) spin_yield(lock)
265 #define arch_read_relax(lock) rw_yield(lock)
266 #define arch_write_relax(lock) rw_yield(lock)
267
268 #endif /* _ASM_POWERPC_SIMPLE_SPINLOCK_H */
269
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.