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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> | |
23 | #include "lockdep.h" | |
24 | #include "include/atomic.h" | |
25 | #include "common/valgrind.h" | |
26 | ||
27 | class RWLock final | |
28 | { | |
29 | mutable pthread_rwlock_t L; | |
30 | std::string name; | |
31 | mutable int id; | |
32 | mutable atomic_t nrlock, nwlock; | |
33 | bool track, lockdep; | |
34 | ||
35 | std::string unique_name(const char* name) const; | |
36 | ||
37 | public: | |
38 | RWLock(const RWLock& other) = delete; | |
39 | const RWLock& operator=(const RWLock& other) = delete; | |
40 | ||
41 | RWLock(const std::string &n, bool track_lock=true, bool ld=true, bool prioritize_write=false) | |
42 | : name(n), id(-1), nrlock(0), nwlock(0), track(track_lock), | |
43 | lockdep(ld) { | |
44 | #if defined(PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP) | |
45 | if (prioritize_write) { | |
46 | pthread_rwlockattr_t attr; | |
47 | pthread_rwlockattr_init(&attr); | |
48 | // PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP | |
49 | // Setting the lock kind to this avoids writer starvation as long as | |
50 | // long as any read locking is not done in a recursive fashion. | |
51 | pthread_rwlockattr_setkind_np(&attr, | |
52 | PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP); | |
53 | pthread_rwlock_init(&L, &attr); | |
54 | } else | |
55 | #endif | |
56 | // Next block is in {} to possibly connect to the above if when code is used. | |
57 | { | |
58 | pthread_rwlock_init(&L, NULL); | |
59 | } | |
60 | ANNOTATE_BENIGN_RACE_SIZED(&id, sizeof(id), "RWLock lockdep id"); | |
61 | ANNOTATE_BENIGN_RACE_SIZED(&nrlock, sizeof(nrlock), "RWlock nrlock"); | |
62 | ANNOTATE_BENIGN_RACE_SIZED(&nwlock, sizeof(nwlock), "RWlock nwlock"); | |
63 | if (lockdep && g_lockdep) id = lockdep_register(name.c_str()); | |
64 | } | |
65 | ||
66 | bool is_locked() const { | |
67 | assert(track); | |
68 | return (nrlock.read() > 0) || (nwlock.read() > 0); | |
69 | } | |
70 | ||
71 | bool is_wlocked() const { | |
72 | assert(track); | |
73 | return (nwlock.read() > 0); | |
74 | } | |
75 | ~RWLock() { | |
76 | // The following check is racy but we are about to destroy | |
77 | // the object and we assume that there are no other users. | |
78 | if (track) | |
79 | assert(!is_locked()); | |
80 | pthread_rwlock_destroy(&L); | |
81 | if (lockdep && g_lockdep) { | |
82 | lockdep_unregister(id); | |
83 | } | |
84 | } | |
85 | ||
86 | void unlock(bool lockdep=true) const { | |
87 | if (track) { | |
88 | if (nwlock.read() > 0) { | |
89 | nwlock.dec(); | |
90 | } else { | |
91 | assert(nrlock.read() > 0); | |
92 | nrlock.dec(); | |
93 | } | |
94 | } | |
95 | if (lockdep && this->lockdep && g_lockdep) | |
96 | id = lockdep_will_unlock(name.c_str(), id); | |
97 | int r = pthread_rwlock_unlock(&L); | |
98 | assert(r == 0); | |
99 | } | |
100 | ||
101 | // read | |
102 | void get_read() const { | |
103 | if (lockdep && g_lockdep) id = lockdep_will_lock(name.c_str(), id); | |
104 | int r = pthread_rwlock_rdlock(&L); | |
105 | assert(r == 0); | |
106 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); | |
107 | if (track) | |
108 | nrlock.inc(); | |
109 | } | |
110 | bool try_get_read() const { | |
111 | if (pthread_rwlock_tryrdlock(&L) == 0) { | |
112 | if (track) | |
113 | nrlock.inc(); | |
114 | if (lockdep && g_lockdep) id = lockdep_locked(name.c_str(), id); | |
115 | return true; | |
116 | } | |
117 | return false; | |
118 | } | |
119 | void put_read() const { | |
120 | unlock(); | |
121 | } | |
122 | ||
123 | // write | |
124 | void get_write(bool lockdep=true) { | |
125 | if (lockdep && this->lockdep && g_lockdep) | |
126 | id = lockdep_will_lock(name.c_str(), id); | |
127 | int r = pthread_rwlock_wrlock(&L); | |
128 | assert(r == 0); | |
129 | if (lockdep && this->lockdep && g_lockdep) | |
130 | id = lockdep_locked(name.c_str(), id); | |
131 | if (track) | |
132 | nwlock.inc(); | |
133 | ||
134 | } | |
135 | bool try_get_write(bool lockdep=true) { | |
136 | if (pthread_rwlock_trywrlock(&L) == 0) { | |
137 | if (lockdep && this->lockdep && g_lockdep) | |
138 | id = lockdep_locked(name.c_str(), id); | |
139 | if (track) | |
140 | nwlock.inc(); | |
141 | return true; | |
142 | } | |
143 | return false; | |
144 | } | |
145 | void put_write() { | |
146 | unlock(); | |
147 | } | |
148 | ||
149 | void get(bool for_write) { | |
150 | if (for_write) { | |
151 | get_write(); | |
152 | } else { | |
153 | get_read(); | |
154 | } | |
155 | } | |
156 | ||
157 | public: | |
158 | class RLocker { | |
159 | const RWLock &m_lock; | |
160 | ||
161 | bool locked; | |
162 | ||
163 | public: | |
164 | explicit RLocker(const RWLock& lock) : m_lock(lock) { | |
165 | m_lock.get_read(); | |
166 | locked = true; | |
167 | } | |
168 | void unlock() { | |
169 | assert(locked); | |
170 | m_lock.unlock(); | |
171 | locked = false; | |
172 | } | |
173 | ~RLocker() { | |
174 | if (locked) { | |
175 | m_lock.unlock(); | |
176 | } | |
177 | } | |
178 | }; | |
179 | ||
180 | class WLocker { | |
181 | RWLock &m_lock; | |
182 | ||
183 | bool locked; | |
184 | ||
185 | public: | |
186 | explicit WLocker(RWLock& lock) : m_lock(lock) { | |
187 | m_lock.get_write(); | |
188 | locked = true; | |
189 | } | |
190 | void unlock() { | |
191 | assert(locked); | |
192 | m_lock.unlock(); | |
193 | locked = false; | |
194 | } | |
195 | ~WLocker() { | |
196 | if (locked) { | |
197 | m_lock.unlock(); | |
198 | } | |
199 | } | |
200 | }; | |
201 | ||
202 | class Context { | |
203 | RWLock& lock; | |
204 | ||
205 | public: | |
206 | enum LockState { | |
207 | Untaken = 0, | |
208 | TakenForRead = 1, | |
209 | TakenForWrite = 2, | |
210 | }; | |
211 | ||
212 | private: | |
213 | LockState state; | |
214 | ||
215 | public: | |
216 | explicit Context(RWLock& l) : lock(l), state(Untaken) {} | |
217 | Context(RWLock& l, LockState s) : lock(l), state(s) {} | |
218 | ||
219 | void get_write() { | |
220 | assert(state == Untaken); | |
221 | ||
222 | lock.get_write(); | |
223 | state = TakenForWrite; | |
224 | } | |
225 | ||
226 | void get_read() { | |
227 | assert(state == Untaken); | |
228 | ||
229 | lock.get_read(); | |
230 | state = TakenForRead; | |
231 | } | |
232 | ||
233 | void unlock() { | |
234 | assert(state != Untaken); | |
235 | lock.unlock(); | |
236 | state = Untaken; | |
237 | } | |
238 | ||
239 | void promote() { | |
240 | assert(state == TakenForRead); | |
241 | unlock(); | |
242 | get_write(); | |
243 | } | |
244 | ||
245 | LockState get_state() { return state; } | |
246 | void set_state(LockState s) { | |
247 | state = s; | |
248 | } | |
249 | ||
250 | bool is_locked() { | |
251 | return (state != Untaken); | |
252 | } | |
253 | ||
254 | bool is_rlocked() { | |
255 | return (state == TakenForRead); | |
256 | } | |
257 | ||
258 | bool is_wlocked() { | |
259 | return (state == TakenForWrite); | |
260 | } | |
261 | }; | |
262 | }; | |
263 | ||
264 | #endif // !CEPH_RWLock_Posix__H |