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1 | // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- |
2 | // vim: ts=8 sw=2 smarttab | |
3 | /* | |
4 | * Ceph - scalable distributed file system | |
5 | * | |
6 | * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net> | |
7 | * | |
8 | * This is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License version 2.1, as published by the Free Software | |
11 | * Foundation. See file COPYING. | |
12 | * | |
13 | */ | |
14 | ||
15 | ||
16 | ||
17 | #ifndef CEPH_RWLock_Posix__H | |
18 | #define CEPH_RWLock_Posix__H | |
19 | ||
20 | #include <pthread.h> | |
21 | #include <string> | |
11fdf7f2 | 22 | #include "include/ceph_assert.h" |
b32b8144 | 23 | #include "acconfig.h" |
7c673cae | 24 | #include "lockdep.h" |
7c673cae FG |
25 | #include "common/valgrind.h" |
26 | ||
31f18b77 FG |
27 | #include <atomic> |
28 | ||
7c673cae FG |
29 | class RWLock final |
30 | { | |
31 | mutable pthread_rwlock_t L; | |
32 | std::string name; | |
33 | mutable int id; | |
31f18b77 | 34 | mutable std::atomic<unsigned> nrlock = { 0 }, nwlock = { 0 }; |
7c673cae FG |
35 | bool track, lockdep; |
36 | ||
37 | std::string unique_name(const char* name) const; | |
38 | ||
39 | public: | |
40 | RWLock(const RWLock& other) = delete; | |
41 | const RWLock& operator=(const RWLock& other) = delete; | |
42 | ||
43 | RWLock(const std::string &n, bool track_lock=true, bool ld=true, bool prioritize_write=false) | |
31f18b77 | 44 | : name(n), id(-1), track(track_lock), |
7c673cae | 45 | lockdep(ld) { |
b32b8144 | 46 | #if defined(HAVE_PTHREAD_RWLOCKATTR_SETKIND_NP) |
7c673cae FG |
47 | if (prioritize_write) { |
48 | pthread_rwlockattr_t attr; | |
49 | pthread_rwlockattr_init(&attr); | |
50 | // PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP | |
51 | // Setting the lock kind to this avoids writer starvation as long as | |
52 | // long as any read locking is not done in a recursive fashion. | |
53 | pthread_rwlockattr_setkind_np(&attr, | |
54 | PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); | |
55 | pthread_rwlock_init(&L, &attr); | |
11fdf7f2 | 56 | pthread_rwlockattr_destroy(&attr); |
7c673cae FG |
57 | } else |
58 | #endif | |
59 | // Next block is in {} to possibly connect to the above if when code is used. | |
60 | { | |
61 | pthread_rwlock_init(&L, NULL); | |
62 | } | |
63 | ANNOTATE_BENIGN_RACE_SIZED(&id, sizeof(id), "RWLock lockdep id"); | |
64 | ANNOTATE_BENIGN_RACE_SIZED(&nrlock, sizeof(nrlock), "RWlock nrlock"); | |
65 | ANNOTATE_BENIGN_RACE_SIZED(&nwlock, sizeof(nwlock), "RWlock nwlock"); | |
66 | if (lockdep && g_lockdep) id = lockdep_register(name.c_str()); | |
67 | } | |
68 | ||
69 | bool is_locked() const { | |
11fdf7f2 | 70 | ceph_assert(track); |
31f18b77 | 71 | return (nrlock > 0) || (nwlock > 0); |
7c673cae FG |
72 | } |
73 | ||
74 | bool is_wlocked() const { | |
11fdf7f2 | 75 | ceph_assert(track); |
31f18b77 | 76 | return (nwlock > 0); |
7c673cae FG |
77 | } |
78 | ~RWLock() { | |
79 | // The following check is racy but we are about to destroy | |
80 | // the object and we assume that there are no other users. | |
81 | if (track) | |
11fdf7f2 | 82 | ceph_assert(!is_locked()); |
7c673cae FG |
83 | pthread_rwlock_destroy(&L); |
84 | if (lockdep && g_lockdep) { | |
85 | lockdep_unregister(id); | |
86 | } | |
87 | } | |
88 | ||
89 | void unlock(bool lockdep=true) const { | |
90 | if (track) { | |
31f18b77 FG |
91 | if (nwlock > 0) { |
92 | nwlock--; | |
7c673cae | 93 | } else { |
11fdf7f2 | 94 | ceph_assert(nrlock > 0); |
31f18b77 | 95 | nrlock--; |
7c673cae FG |
96 | } |
97 | } | |
98 | if (lockdep && this->lockdep && g_lockdep) | |
99 | id = lockdep_will_unlock(name.c_str(), id); | |
100 | int r = pthread_rwlock_unlock(&L); | |
11fdf7f2 | 101 | ceph_assert(r == 0); |
7c673cae FG |
102 | } |
103 | ||
104 | // read | |
105 | void get_read() const { | |
106 | if (lockdep && g_lockdep) id = lockdep_will_lock(name.c_str(), id); | |
107 | int r = pthread_rwlock_rdlock(&L); | |
11fdf7f2 | 108 | ceph_assert(r == 0); |
7c673cae FG |
109 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); |
110 | if (track) | |
31f18b77 | 111 | nrlock++; |
7c673cae FG |
112 | } |
113 | bool try_get_read() const { | |
114 | if (pthread_rwlock_tryrdlock(&L) == 0) { | |
115 | if (track) | |
31f18b77 | 116 | nrlock++; |
7c673cae FG |
117 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); |
118 | return true; | |
119 | } | |
120 | return false; | |
121 | } | |
122 | void put_read() const { | |
123 | unlock(); | |
124 | } | |
9f95a23c TL |
125 | void lock_shared() { |
126 | get_read(); | |
127 | } | |
128 | void unlock_shared() { | |
129 | put_read(); | |
130 | } | |
7c673cae FG |
131 | // write |
132 | void get_write(bool lockdep=true) { | |
133 | if (lockdep && this->lockdep && g_lockdep) | |
134 | id = lockdep_will_lock(name.c_str(), id); | |
135 | int r = pthread_rwlock_wrlock(&L); | |
11fdf7f2 | 136 | ceph_assert(r == 0); |
7c673cae FG |
137 | if (lockdep && this->lockdep && g_lockdep) |
138 | id = lockdep_locked(name.c_str(), id); | |
139 | if (track) | |
31f18b77 | 140 | nwlock++; |
7c673cae FG |
141 | |
142 | } | |
143 | bool try_get_write(bool lockdep=true) { | |
144 | if (pthread_rwlock_trywrlock(&L) == 0) { | |
145 | if (lockdep && this->lockdep && g_lockdep) | |
146 | id = lockdep_locked(name.c_str(), id); | |
147 | if (track) | |
31f18b77 | 148 | nwlock++; |
7c673cae FG |
149 | return true; |
150 | } | |
151 | return false; | |
152 | } | |
153 | void put_write() { | |
154 | unlock(); | |
155 | } | |
9f95a23c TL |
156 | void lock() { |
157 | get_write(); | |
158 | } | |
7c673cae FG |
159 | void get(bool for_write) { |
160 | if (for_write) { | |
161 | get_write(); | |
162 | } else { | |
163 | get_read(); | |
164 | } | |
165 | } | |
166 | ||
167 | public: | |
168 | class RLocker { | |
169 | const RWLock &m_lock; | |
170 | ||
171 | bool locked; | |
172 | ||
173 | public: | |
174 | explicit RLocker(const RWLock& lock) : m_lock(lock) { | |
175 | m_lock.get_read(); | |
176 | locked = true; | |
177 | } | |
178 | void unlock() { | |
11fdf7f2 | 179 | ceph_assert(locked); |
7c673cae FG |
180 | m_lock.unlock(); |
181 | locked = false; | |
182 | } | |
183 | ~RLocker() { | |
184 | if (locked) { | |
185 | m_lock.unlock(); | |
186 | } | |
187 | } | |
188 | }; | |
189 | ||
190 | class WLocker { | |
191 | RWLock &m_lock; | |
192 | ||
193 | bool locked; | |
194 | ||
195 | public: | |
196 | explicit WLocker(RWLock& lock) : m_lock(lock) { | |
197 | m_lock.get_write(); | |
198 | locked = true; | |
199 | } | |
200 | void unlock() { | |
11fdf7f2 | 201 | ceph_assert(locked); |
7c673cae FG |
202 | m_lock.unlock(); |
203 | locked = false; | |
204 | } | |
205 | ~WLocker() { | |
206 | if (locked) { | |
207 | m_lock.unlock(); | |
208 | } | |
209 | } | |
210 | }; | |
211 | ||
212 | class Context { | |
213 | RWLock& lock; | |
214 | ||
215 | public: | |
216 | enum LockState { | |
217 | Untaken = 0, | |
218 | TakenForRead = 1, | |
219 | TakenForWrite = 2, | |
220 | }; | |
221 | ||
222 | private: | |
223 | LockState state; | |
224 | ||
225 | public: | |
226 | explicit Context(RWLock& l) : lock(l), state(Untaken) {} | |
227 | Context(RWLock& l, LockState s) : lock(l), state(s) {} | |
228 | ||
229 | void get_write() { | |
11fdf7f2 | 230 | ceph_assert(state == Untaken); |
7c673cae FG |
231 | |
232 | lock.get_write(); | |
233 | state = TakenForWrite; | |
234 | } | |
235 | ||
236 | void get_read() { | |
11fdf7f2 | 237 | ceph_assert(state == Untaken); |
7c673cae FG |
238 | |
239 | lock.get_read(); | |
240 | state = TakenForRead; | |
241 | } | |
242 | ||
243 | void unlock() { | |
11fdf7f2 | 244 | ceph_assert(state != Untaken); |
7c673cae FG |
245 | lock.unlock(); |
246 | state = Untaken; | |
247 | } | |
248 | ||
249 | void promote() { | |
11fdf7f2 | 250 | ceph_assert(state == TakenForRead); |
7c673cae FG |
251 | unlock(); |
252 | get_write(); | |
253 | } | |
254 | ||
255 | LockState get_state() { return state; } | |
256 | void set_state(LockState s) { | |
257 | state = s; | |
258 | } | |
259 | ||
260 | bool is_locked() { | |
261 | return (state != Untaken); | |
262 | } | |
263 | ||
264 | bool is_rlocked() { | |
265 | return (state == TakenForRead); | |
266 | } | |
267 | ||
268 | bool is_wlocked() { | |
269 | return (state == TakenForWrite); | |
270 | } | |
271 | }; | |
272 | }; | |
273 | ||
274 | #endif // !CEPH_RWLock_Posix__H |