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6e35fa2d VG |
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 | #define arch_spin_unlock_wait(x) \ | |
19 | do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0) | |
20 | ||
ae7eae9e VG |
21 | #ifdef CONFIG_ARC_HAS_LLSC |
22 | ||
23 | static inline void arch_spin_lock(arch_spinlock_t *lock) | |
24 | { | |
25 | unsigned int val; | |
26 | ||
27 | smp_mb(); | |
28 | ||
29 | __asm__ __volatile__( | |
30 | "1: llock %[val], [%[slock]] \n" | |
31 | " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */ | |
32 | " scond %[LOCKED], [%[slock]] \n" /* acquire */ | |
33 | " bnz 1b \n" | |
34 | " \n" | |
35 | : [val] "=&r" (val) | |
36 | : [slock] "r" (&(lock->slock)), | |
37 | [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) | |
38 | : "memory", "cc"); | |
39 | ||
40 | smp_mb(); | |
41 | } | |
42 | ||
43 | /* 1 - lock taken successfully */ | |
44 | static inline int arch_spin_trylock(arch_spinlock_t *lock) | |
45 | { | |
46 | unsigned int val, got_it = 0; | |
47 | ||
48 | smp_mb(); | |
49 | ||
50 | __asm__ __volatile__( | |
51 | "1: llock %[val], [%[slock]] \n" | |
52 | " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */ | |
53 | " scond %[LOCKED], [%[slock]] \n" /* acquire */ | |
54 | " bnz 1b \n" | |
55 | " mov %[got_it], 1 \n" | |
56 | "4: \n" | |
57 | " \n" | |
58 | : [val] "=&r" (val), | |
59 | [got_it] "+&r" (got_it) | |
60 | : [slock] "r" (&(lock->slock)), | |
61 | [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) | |
62 | : "memory", "cc"); | |
63 | ||
64 | smp_mb(); | |
65 | ||
66 | return got_it; | |
67 | } | |
68 | ||
69 | static inline void arch_spin_unlock(arch_spinlock_t *lock) | |
70 | { | |
71 | smp_mb(); | |
72 | ||
73 | lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__; | |
74 | ||
75 | smp_mb(); | |
76 | } | |
77 | ||
78 | #else /* !CONFIG_ARC_HAS_LLSC */ | |
79 | ||
6e35fa2d VG |
80 | static inline void arch_spin_lock(arch_spinlock_t *lock) |
81 | { | |
ae7eae9e | 82 | unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; |
6e35fa2d | 83 | |
2576c28e VG |
84 | /* |
85 | * This smp_mb() is technically superfluous, we only need the one | |
86 | * after the lock for providing the ACQUIRE semantics. | |
87 | * However doing the "right" thing was regressing hackbench | |
88 | * so keeping this, pending further investigation | |
89 | */ | |
90 | smp_mb(); | |
91 | ||
6e35fa2d VG |
92 | __asm__ __volatile__( |
93 | "1: ex %0, [%1] \n" | |
94 | " breq %0, %2, 1b \n" | |
ae7eae9e | 95 | : "+&r" (val) |
6e35fa2d VG |
96 | : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__) |
97 | : "memory"); | |
2576c28e VG |
98 | |
99 | /* | |
100 | * ACQUIRE barrier to ensure load/store after taking the lock | |
101 | * don't "bleed-up" out of the critical section (leak-in is allowed) | |
102 | * http://www.spinics.net/lists/kernel/msg2010409.html | |
103 | * | |
104 | * ARCv2 only has load-load, store-store and all-all barrier | |
105 | * thus need the full all-all barrier | |
106 | */ | |
107 | smp_mb(); | |
6e35fa2d VG |
108 | } |
109 | ||
ae7eae9e | 110 | /* 1 - lock taken successfully */ |
6e35fa2d VG |
111 | static inline int arch_spin_trylock(arch_spinlock_t *lock) |
112 | { | |
ae7eae9e | 113 | unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; |
6e35fa2d | 114 | |
2576c28e VG |
115 | smp_mb(); |
116 | ||
6e35fa2d VG |
117 | __asm__ __volatile__( |
118 | "1: ex %0, [%1] \n" | |
ae7eae9e | 119 | : "+r" (val) |
6e35fa2d VG |
120 | : "r"(&(lock->slock)) |
121 | : "memory"); | |
122 | ||
2576c28e VG |
123 | smp_mb(); |
124 | ||
ae7eae9e | 125 | return (val == __ARCH_SPIN_LOCK_UNLOCKED__); |
6e35fa2d VG |
126 | } |
127 | ||
128 | static inline void arch_spin_unlock(arch_spinlock_t *lock) | |
129 | { | |
ae7eae9e | 130 | unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__; |
6c00350b | 131 | |
2576c28e VG |
132 | /* |
133 | * RELEASE barrier: given the instructions avail on ARCv2, full barrier | |
134 | * is the only option | |
135 | */ | |
136 | smp_mb(); | |
137 | ||
6c00350b VG |
138 | __asm__ __volatile__( |
139 | " ex %0, [%1] \n" | |
ae7eae9e | 140 | : "+r" (val) |
6c00350b VG |
141 | : "r"(&(lock->slock)) |
142 | : "memory"); | |
143 | ||
2576c28e VG |
144 | /* |
145 | * superfluous, but keeping for now - see pairing version in | |
146 | * arch_spin_lock above | |
147 | */ | |
6e35fa2d VG |
148 | smp_mb(); |
149 | } | |
150 | ||
ae7eae9e VG |
151 | #endif |
152 | ||
6e35fa2d VG |
153 | /* |
154 | * Read-write spinlocks, allowing multiple readers but only one writer. | |
155 | * | |
156 | * The spinlock itself is contained in @counter and access to it is | |
157 | * serialized with @lock_mutex. | |
158 | * | |
159 | * Unfair locking as Writers could be starved indefinitely by Reader(s) | |
160 | */ | |
161 | ||
162 | /* Would read_trylock() succeed? */ | |
163 | #define arch_read_can_lock(x) ((x)->counter > 0) | |
164 | ||
165 | /* Would write_trylock() succeed? */ | |
166 | #define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__) | |
167 | ||
168 | /* 1 - lock taken successfully */ | |
169 | static inline int arch_read_trylock(arch_rwlock_t *rw) | |
170 | { | |
171 | int ret = 0; | |
172 | ||
173 | arch_spin_lock(&(rw->lock_mutex)); | |
174 | ||
175 | /* | |
176 | * zero means writer holds the lock exclusively, deny Reader. | |
177 | * Otherwise grant lock to first/subseq reader | |
178 | */ | |
179 | if (rw->counter > 0) { | |
180 | rw->counter--; | |
181 | ret = 1; | |
182 | } | |
183 | ||
184 | arch_spin_unlock(&(rw->lock_mutex)); | |
185 | ||
186 | smp_mb(); | |
187 | return ret; | |
188 | } | |
189 | ||
190 | /* 1 - lock taken successfully */ | |
191 | static inline int arch_write_trylock(arch_rwlock_t *rw) | |
192 | { | |
193 | int ret = 0; | |
194 | ||
195 | arch_spin_lock(&(rw->lock_mutex)); | |
196 | ||
197 | /* | |
198 | * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), | |
199 | * deny writer. Otherwise if unlocked grant to writer | |
200 | * Hence the claim that Linux rwlocks are unfair to writers. | |
201 | * (can be starved for an indefinite time by readers). | |
202 | */ | |
203 | if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) { | |
204 | rw->counter = 0; | |
205 | ret = 1; | |
206 | } | |
207 | arch_spin_unlock(&(rw->lock_mutex)); | |
208 | ||
209 | return ret; | |
210 | } | |
211 | ||
212 | static inline void arch_read_lock(arch_rwlock_t *rw) | |
213 | { | |
214 | while (!arch_read_trylock(rw)) | |
215 | cpu_relax(); | |
216 | } | |
217 | ||
218 | static inline void arch_write_lock(arch_rwlock_t *rw) | |
219 | { | |
220 | while (!arch_write_trylock(rw)) | |
221 | cpu_relax(); | |
222 | } | |
223 | ||
224 | static inline void arch_read_unlock(arch_rwlock_t *rw) | |
225 | { | |
226 | arch_spin_lock(&(rw->lock_mutex)); | |
227 | rw->counter++; | |
228 | arch_spin_unlock(&(rw->lock_mutex)); | |
229 | } | |
230 | ||
231 | static inline void arch_write_unlock(arch_rwlock_t *rw) | |
232 | { | |
233 | arch_spin_lock(&(rw->lock_mutex)); | |
234 | rw->counter = __ARCH_RW_LOCK_UNLOCKED__; | |
235 | arch_spin_unlock(&(rw->lock_mutex)); | |
236 | } | |
237 | ||
238 | #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) | |
239 | #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) | |
240 | ||
241 | #define arch_spin_relax(lock) cpu_relax() | |
242 | #define arch_read_relax(lock) cpu_relax() | |
243 | #define arch_write_relax(lock) cpu_relax() | |
244 | ||
245 | #endif /* __ASM_SPINLOCK_H */ |