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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> | |
22 | #include <include/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); | |
56 | } else | |
57 | #endif | |
58 | // Next block is in {} to possibly connect to the above if when code is used. | |
59 | { | |
60 | pthread_rwlock_init(&L, NULL); | |
61 | } | |
62 | ANNOTATE_BENIGN_RACE_SIZED(&id, sizeof(id), "RWLock lockdep id"); | |
63 | ANNOTATE_BENIGN_RACE_SIZED(&nrlock, sizeof(nrlock), "RWlock nrlock"); | |
64 | ANNOTATE_BENIGN_RACE_SIZED(&nwlock, sizeof(nwlock), "RWlock nwlock"); | |
65 | if (lockdep && g_lockdep) id = lockdep_register(name.c_str()); | |
66 | } | |
67 | ||
68 | bool is_locked() const { | |
69 | assert(track); | |
31f18b77 | 70 | return (nrlock > 0) || (nwlock > 0); |
7c673cae FG |
71 | } |
72 | ||
73 | bool is_wlocked() const { | |
74 | assert(track); | |
31f18b77 | 75 | return (nwlock > 0); |
7c673cae FG |
76 | } |
77 | ~RWLock() { | |
78 | // The following check is racy but we are about to destroy | |
79 | // the object and we assume that there are no other users. | |
80 | if (track) | |
81 | assert(!is_locked()); | |
82 | pthread_rwlock_destroy(&L); | |
83 | if (lockdep && g_lockdep) { | |
84 | lockdep_unregister(id); | |
85 | } | |
86 | } | |
87 | ||
88 | void unlock(bool lockdep=true) const { | |
89 | if (track) { | |
31f18b77 FG |
90 | if (nwlock > 0) { |
91 | nwlock--; | |
7c673cae | 92 | } else { |
31f18b77 FG |
93 | assert(nrlock > 0); |
94 | nrlock--; | |
7c673cae FG |
95 | } |
96 | } | |
97 | if (lockdep && this->lockdep && g_lockdep) | |
98 | id = lockdep_will_unlock(name.c_str(), id); | |
99 | int r = pthread_rwlock_unlock(&L); | |
100 | assert(r == 0); | |
101 | } | |
102 | ||
103 | // read | |
104 | void get_read() const { | |
105 | if (lockdep && g_lockdep) id = lockdep_will_lock(name.c_str(), id); | |
106 | int r = pthread_rwlock_rdlock(&L); | |
107 | assert(r == 0); | |
108 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); | |
109 | if (track) | |
31f18b77 | 110 | nrlock++; |
7c673cae FG |
111 | } |
112 | bool try_get_read() const { | |
113 | if (pthread_rwlock_tryrdlock(&L) == 0) { | |
114 | if (track) | |
31f18b77 | 115 | nrlock++; |
7c673cae FG |
116 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); |
117 | return true; | |
118 | } | |
119 | return false; | |
120 | } | |
121 | void put_read() const { | |
122 | unlock(); | |
123 | } | |
124 | ||
125 | // write | |
126 | void get_write(bool lockdep=true) { | |
127 | if (lockdep && this->lockdep && g_lockdep) | |
128 | id = lockdep_will_lock(name.c_str(), id); | |
129 | int r = pthread_rwlock_wrlock(&L); | |
130 | assert(r == 0); | |
131 | if (lockdep && this->lockdep && g_lockdep) | |
132 | id = lockdep_locked(name.c_str(), id); | |
133 | if (track) | |
31f18b77 | 134 | nwlock++; |
7c673cae FG |
135 | |
136 | } | |
137 | bool try_get_write(bool lockdep=true) { | |
138 | if (pthread_rwlock_trywrlock(&L) == 0) { | |
139 | if (lockdep && this->lockdep && g_lockdep) | |
140 | id = lockdep_locked(name.c_str(), id); | |
141 | if (track) | |
31f18b77 | 142 | nwlock++; |
7c673cae FG |
143 | return true; |
144 | } | |
145 | return false; | |
146 | } | |
147 | void put_write() { | |
148 | unlock(); | |
149 | } | |
150 | ||
151 | void get(bool for_write) { | |
152 | if (for_write) { | |
153 | get_write(); | |
154 | } else { | |
155 | get_read(); | |
156 | } | |
157 | } | |
158 | ||
159 | public: | |
160 | class RLocker { | |
161 | const RWLock &m_lock; | |
162 | ||
163 | bool locked; | |
164 | ||
165 | public: | |
166 | explicit RLocker(const RWLock& lock) : m_lock(lock) { | |
167 | m_lock.get_read(); | |
168 | locked = true; | |
169 | } | |
170 | void unlock() { | |
171 | assert(locked); | |
172 | m_lock.unlock(); | |
173 | locked = false; | |
174 | } | |
175 | ~RLocker() { | |
176 | if (locked) { | |
177 | m_lock.unlock(); | |
178 | } | |
179 | } | |
180 | }; | |
181 | ||
182 | class WLocker { | |
183 | RWLock &m_lock; | |
184 | ||
185 | bool locked; | |
186 | ||
187 | public: | |
188 | explicit WLocker(RWLock& lock) : m_lock(lock) { | |
189 | m_lock.get_write(); | |
190 | locked = true; | |
191 | } | |
192 | void unlock() { | |
193 | assert(locked); | |
194 | m_lock.unlock(); | |
195 | locked = false; | |
196 | } | |
197 | ~WLocker() { | |
198 | if (locked) { | |
199 | m_lock.unlock(); | |
200 | } | |
201 | } | |
202 | }; | |
203 | ||
204 | class Context { | |
205 | RWLock& lock; | |
206 | ||
207 | public: | |
208 | enum LockState { | |
209 | Untaken = 0, | |
210 | TakenForRead = 1, | |
211 | TakenForWrite = 2, | |
212 | }; | |
213 | ||
214 | private: | |
215 | LockState state; | |
216 | ||
217 | public: | |
218 | explicit Context(RWLock& l) : lock(l), state(Untaken) {} | |
219 | Context(RWLock& l, LockState s) : lock(l), state(s) {} | |
220 | ||
221 | void get_write() { | |
222 | assert(state == Untaken); | |
223 | ||
224 | lock.get_write(); | |
225 | state = TakenForWrite; | |
226 | } | |
227 | ||
228 | void get_read() { | |
229 | assert(state == Untaken); | |
230 | ||
231 | lock.get_read(); | |
232 | state = TakenForRead; | |
233 | } | |
234 | ||
235 | void unlock() { | |
236 | assert(state != Untaken); | |
237 | lock.unlock(); | |
238 | state = Untaken; | |
239 | } | |
240 | ||
241 | void promote() { | |
242 | assert(state == TakenForRead); | |
243 | unlock(); | |
244 | get_write(); | |
245 | } | |
246 | ||
247 | LockState get_state() { return state; } | |
248 | void set_state(LockState s) { | |
249 | state = s; | |
250 | } | |
251 | ||
252 | bool is_locked() { | |
253 | return (state != Untaken); | |
254 | } | |
255 | ||
256 | bool is_rlocked() { | |
257 | return (state == TakenForRead); | |
258 | } | |
259 | ||
260 | bool is_wlocked() { | |
261 | return (state == TakenForWrite); | |
262 | } | |
263 | }; | |
264 | }; | |
265 | ||
266 | #endif // !CEPH_RWLock_Posix__H |