Branch data Line data Source code
1 : : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : : // Copyright (c) 2009-2022 The Bitcoin Core developers
3 : : // Distributed under the MIT software license, see the accompanying
4 : : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5 : :
6 : : #ifndef BITCOIN_SYNC_H
7 : : #define BITCOIN_SYNC_H
8 : :
9 : : #ifdef DEBUG_LOCKCONTENTION
10 : : #include <logging.h>
11 : : #include <logging/timer.h>
12 : : #endif
13 : :
14 : : #include <threadsafety.h> // IWYU pragma: export
15 : : #include <util/macros.h>
16 : :
17 : : #include <condition_variable>
18 : : #include <mutex>
19 : : #include <string>
20 : : #include <thread>
21 : :
22 : : ////////////////////////////////////////////////
23 : : // //
24 : : // THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
25 : : // //
26 : : ////////////////////////////////////////////////
27 : :
28 : : /*
29 : : RecursiveMutex mutex;
30 : : std::recursive_mutex mutex;
31 : :
32 : : LOCK(mutex);
33 : : std::unique_lock<std::recursive_mutex> criticalblock(mutex);
34 : :
35 : : LOCK2(mutex1, mutex2);
36 : : std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
37 : : std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
38 : :
39 : : TRY_LOCK(mutex, name);
40 : : std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
41 : :
42 : : ENTER_CRITICAL_SECTION(mutex); // no RAII
43 : : mutex.lock();
44 : :
45 : : LEAVE_CRITICAL_SECTION(mutex); // no RAII
46 : : mutex.unlock();
47 : : */
48 : :
49 : : ///////////////////////////////
50 : : // //
51 : : // THE ACTUAL IMPLEMENTATION //
52 : : // //
53 : : ///////////////////////////////
54 : :
55 : : #ifdef DEBUG_LOCKORDER
56 : : template <typename MutexType>
57 : : void EnterCritical(const char* pszName, const char* pszFile, int nLine, MutexType* cs, bool fTry = false);
58 : : void LeaveCritical();
59 : : void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line);
60 : : template <typename MutexType>
61 : : void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) EXCLUSIVE_LOCKS_REQUIRED(cs);
62 : : template <typename MutexType>
63 : : void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) LOCKS_EXCLUDED(cs);
64 : : void DeleteLock(void* cs);
65 : : bool LockStackEmpty();
66 : :
67 : : /**
68 : : * Call abort() if a potential lock order deadlock bug is detected, instead of
69 : : * just logging information and throwing a logic_error. Defaults to true, and
70 : : * set to false in DEBUG_LOCKORDER unit tests.
71 : : */
72 : : extern bool g_debug_lockorder_abort;
73 : : #else
74 : : template <typename MutexType>
75 : 0 : inline void EnterCritical(const char* pszName, const char* pszFile, int nLine, MutexType* cs, bool fTry = false) {}
76 [ # # # # : 10 : inline void LeaveCritical() {}
# # # # #
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77 : 0 : inline void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line) {}
78 : : template <typename MutexType>
79 : 0 : inline void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) EXCLUSIVE_LOCKS_REQUIRED(cs) {}
80 : : template <typename MutexType>
81 : : void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) LOCKS_EXCLUDED(cs) {}
82 : 12 : inline void DeleteLock(void* cs) {}
83 : : inline bool LockStackEmpty() { return true; }
84 : : #endif
85 : :
86 : : /**
87 : : * Template mixin that adds -Wthread-safety locking annotations and lock order
88 : : * checking to a subset of the mutex API.
89 : : */
90 : : template <typename PARENT>
91 [ # # # # ]: 8 : class LOCKABLE AnnotatedMixin : public PARENT
[ # # ][ # #
# # # # #
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# # ]
92 : : {
93 : : public:
94 : 12 : ~AnnotatedMixin() {
95 : 12 : DeleteLock((void*)this);
96 : 10 : }
97 : :
98 : 0 : void lock() EXCLUSIVE_LOCK_FUNCTION()
99 : : {
100 [ # # ]: 0 : PARENT::lock();
101 : 0 : }
102 : :
103 : 0 : void unlock() UNLOCK_FUNCTION()
104 : : {
105 : 0 : PARENT::unlock();
106 : : }
107 : :
108 : : bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true)
109 : : {
110 : : return PARENT::try_lock();
111 : : }
112 : :
113 : : using unique_lock = std::unique_lock<PARENT>;
114 : : #ifdef __clang__
115 : : //! For negative capabilities in the Clang Thread Safety Analysis.
116 : : //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
117 : : //! with the ! operator, to indicate that a mutex should not be held.
118 : : const AnnotatedMixin& operator!() const { return *this; }
119 : : #endif // __clang__
120 : : };
121 : :
122 : : /**
123 : : * Wrapped mutex: supports recursive locking, but no waiting
124 : : * TODO: We should move away from using the recursive lock by default.
125 : : */
126 : : using RecursiveMutex = AnnotatedMixin<std::recursive_mutex>;
127 : :
128 : : /** Wrapped mutex: supports waiting but not recursive locking */
129 : : using Mutex = AnnotatedMixin<std::mutex>;
130 : :
131 : : /** Different type to mark Mutex at global scope
132 : : *
133 : : * Thread safety analysis can't handle negative assertions about mutexes
134 : : * with global scope well, so mark them with a separate type, and
135 : : * eventually move all the mutexes into classes so they are not globally
136 : : * visible.
137 : : *
138 : : * See: https://github.com/bitcoin/bitcoin/pull/20272#issuecomment-720755781
139 : : */
140 : : class GlobalMutex : public Mutex { };
141 : :
142 : : #define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
143 : :
144 : 0 : inline void AssertLockNotHeldInline(const char* name, const char* file, int line, Mutex* cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) { AssertLockNotHeldInternal(name, file, line, cs); }
145 : : inline void AssertLockNotHeldInline(const char* name, const char* file, int line, RecursiveMutex* cs) LOCKS_EXCLUDED(cs) { AssertLockNotHeldInternal(name, file, line, cs); }
146 : : inline void AssertLockNotHeldInline(const char* name, const char* file, int line, GlobalMutex* cs) LOCKS_EXCLUDED(cs) { AssertLockNotHeldInternal(name, file, line, cs); }
147 : : #define AssertLockNotHeld(cs) AssertLockNotHeldInline(#cs, __FILE__, __LINE__, &cs)
148 : :
149 : : /** Wrapper around std::unique_lock style lock for MutexType. */
150 : : template <typename MutexType>
151 : : class SCOPED_LOCKABLE UniqueLock : public MutexType::unique_lock
152 : : {
153 : : private:
154 : : using Base = typename MutexType::unique_lock;
155 : :
156 : 10 : void Enter(const char* pszName, const char* pszFile, int nLine)
157 : : {
158 : 10 : EnterCritical(pszName, pszFile, nLine, Base::mutex());
159 : : #ifdef DEBUG_LOCKCONTENTION
160 : : if (Base::try_lock()) return;
161 : : LOG_TIME_MICROS_WITH_CATEGORY(strprintf("lock contention %s, %s:%d", pszName, pszFile, nLine), BCLog::LOCK);
162 : : #endif
163 [ + - ][ # # : 10 : Base::lock();
# # # # ]
[ # # # # ]
164 : 10 : }
165 : :
166 : 0 : bool TryEnter(const char* pszName, const char* pszFile, int nLine)
167 : : {
168 : 0 : EnterCritical(pszName, pszFile, nLine, Base::mutex(), true);
169 [ # # ][ # # : 0 : if (Base::try_lock()) {
# # # # ]
[ # # # # ]
170 : : return true;
171 : : }
172 : : LeaveCritical();
173 : : return false;
174 : : }
175 : :
176 : : public:
177 [ - + ]: 10 : UniqueLock(MutexType& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : Base(mutexIn, std::defer_lock)
178 : : {
179 [ - + ]: 10 : if (fTry)
180 : 10 : TryEnter(pszName, pszFile, nLine);
181 : : else
182 : 10 : Enter(pszName, pszFile, nLine);
183 [ - - ]: 10 : }
184 : :
185 : 0 : UniqueLock(MutexType* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
186 [ # # ]: 0 : {
187 [ # # ]: 0 : if (!pmutexIn) return;
188 : :
189 [ # # ]: 0 : *static_cast<Base*>(this) = Base(*pmutexIn, std::defer_lock);
190 [ # # ]: 0 : if (fTry)
191 : 0 : TryEnter(pszName, pszFile, nLine);
192 : : else
193 : 0 : Enter(pszName, pszFile, nLine);
194 [ - - ]: 0 : }
195 : :
196 : 10 : ~UniqueLock() UNLOCK_FUNCTION()
197 : : {
198 [ # # # # : 10 : if (Base::owns_lock())
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201 : :
202 : 0 : operator bool()
203 : : {
204 [ # # # # ]: 0 : return Base::owns_lock();
[ # # ]
205 : : }
206 : :
207 : : protected:
208 : : // needed for reverse_lock
209 : 0 : UniqueLock() = default;
210 : :
211 : : public:
212 : : /**
213 : : * An RAII-style reverse lock. Unlocks on construction and locks on destruction.
214 : : */
215 : : class reverse_lock {
216 : : public:
217 [ # # ]: 0 : explicit reverse_lock(UniqueLock& _lock, const char* _guardname, const char* _file, int _line) : lock(_lock), file(_file), line(_line) {
218 [ # # ]: 0 : CheckLastCritical((void*)lock.mutex(), lockname, _guardname, _file, _line);
219 [ # # ]: 0 : lock.unlock();
220 : : LeaveCritical();
221 : 0 : lock.swap(templock);
222 [ # # ]: 0 : }
223 : :
224 : 0 : ~reverse_lock() {
225 : 0 : templock.swap(lock);
226 : 0 : EnterCritical(lockname.c_str(), file.c_str(), line, lock.mutex());
227 : 0 : lock.lock();
228 [ # # ]: 0 : }
229 : :
230 : : private:
231 : : reverse_lock(reverse_lock const&);
232 : : reverse_lock& operator=(reverse_lock const&);
233 : :
234 : : UniqueLock& lock;
235 : : UniqueLock templock;
236 : : std::string lockname;
237 : : const std::string file;
238 : : const int line;
239 : : };
240 : : friend class reverse_lock;
241 : : };
242 : :
243 : : #define REVERSE_LOCK(g) typename std::decay<decltype(g)>::type::reverse_lock UNIQUE_NAME(revlock)(g, #g, __FILE__, __LINE__)
244 : :
245 : : // When locking a Mutex, require negative capability to ensure the lock
246 : : // is not already held
247 [ # # ]: 0 : inline Mutex& MaybeCheckNotHeld(Mutex& cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) LOCK_RETURNED(cs) { return cs; }
248 : : inline Mutex* MaybeCheckNotHeld(Mutex* cs) EXCLUSIVE_LOCKS_REQUIRED(!cs) LOCK_RETURNED(cs) { return cs; }
249 : :
250 : : // When locking a GlobalMutex or RecursiveMutex, just check it is not
251 : : // locked in the surrounding scope.
252 : : template <typename MutexType>
253 [ # # ]: 0 : inline MutexType& MaybeCheckNotHeld(MutexType& m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
254 : : template <typename MutexType>
255 : : inline MutexType* MaybeCheckNotHeld(MutexType* m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
256 : :
257 : : #define LOCK(cs) UniqueLock UNIQUE_NAME(criticalblock)(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
258 : : #define LOCK2(cs1, cs2) \
259 : : UniqueLock criticalblock1(MaybeCheckNotHeld(cs1), #cs1, __FILE__, __LINE__); \
260 : : UniqueLock criticalblock2(MaybeCheckNotHeld(cs2), #cs2, __FILE__, __LINE__)
261 : : #define TRY_LOCK(cs, name) UniqueLock name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__, true)
262 : : #define WAIT_LOCK(cs, name) UniqueLock name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
263 : :
264 : : #define ENTER_CRITICAL_SECTION(cs) \
265 : : { \
266 : : EnterCritical(#cs, __FILE__, __LINE__, &cs); \
267 : : (cs).lock(); \
268 : : }
269 : :
270 : : #define LEAVE_CRITICAL_SECTION(cs) \
271 : : { \
272 : : std::string lockname; \
273 : : CheckLastCritical((void*)(&cs), lockname, #cs, __FILE__, __LINE__); \
274 : : (cs).unlock(); \
275 : : LeaveCritical(); \
276 : : }
277 : :
278 : : //! Run code while locking a mutex.
279 : : //!
280 : : //! Examples:
281 : : //!
282 : : //! WITH_LOCK(cs, shared_val = shared_val + 1);
283 : : //!
284 : : //! int val = WITH_LOCK(cs, return shared_val);
285 : : //!
286 : : //! Note:
287 : : //!
288 : : //! Since the return type deduction follows that of decltype(auto), while the
289 : : //! deduced type of:
290 : : //!
291 : : //! WITH_LOCK(cs, return {int i = 1; return i;});
292 : : //!
293 : : //! is int, the deduced type of:
294 : : //!
295 : : //! WITH_LOCK(cs, return {int j = 1; return (j);});
296 : : //!
297 : : //! is &int, a reference to a local variable
298 : : //!
299 : : //! The above is detectable at compile-time with the -Wreturn-local-addr flag in
300 : : //! gcc and the -Wreturn-stack-address flag in clang, both enabled by default.
301 : : #define WITH_LOCK(cs, code) (MaybeCheckNotHeld(cs), [&]() -> decltype(auto) { LOCK(cs); code; }())
302 : :
303 : : /** An implementation of a semaphore.
304 : : *
305 : : * See https://en.wikipedia.org/wiki/Semaphore_(programming)
306 : : */
307 : 0 : class CSemaphore
308 : : {
309 : : private:
310 : : std::condition_variable condition;
311 : : std::mutex mutex;
312 : : int value;
313 : :
314 : : public:
315 [ # # ]: 0 : explicit CSemaphore(int init) noexcept : value(init) {}
316 : :
317 : : // Disallow default construct, copy, move.
318 : : CSemaphore() = delete;
319 : : CSemaphore(const CSemaphore&) = delete;
320 : : CSemaphore(CSemaphore&&) = delete;
321 : : CSemaphore& operator=(const CSemaphore&) = delete;
322 : : CSemaphore& operator=(CSemaphore&&) = delete;
323 : :
324 : 0 : void wait() noexcept
325 : : {
326 : 0 : std::unique_lock<std::mutex> lock(mutex);
327 [ # # ]: 0 : condition.wait(lock, [&]() { return value >= 1; });
328 [ # # ]: 0 : value--;
329 : 0 : }
330 : :
331 : 0 : bool try_wait() noexcept
332 : : {
333 : 0 : std::lock_guard<std::mutex> lock(mutex);
334 [ # # ]: 0 : if (value < 1) {
335 : : return false;
336 : : }
337 : 0 : value--;
338 : 0 : return true;
339 : 0 : }
340 : :
341 : 0 : void post() noexcept
342 : : {
343 : 0 : {
344 : 0 : std::lock_guard<std::mutex> lock(mutex);
345 : 0 : value++;
346 : 0 : }
347 : 0 : condition.notify_one();
348 : 0 : }
349 : : };
350 : :
351 : : /** RAII-style semaphore lock */
352 : : class CSemaphoreGrant
353 : : {
354 : : private:
355 : : CSemaphore* sem;
356 : : bool fHaveGrant;
357 : :
358 : : public:
359 : 0 : void Acquire() noexcept
360 : : {
361 [ # # ]: 0 : if (fHaveGrant) {
362 : : return;
363 : : }
364 : 0 : sem->wait();
365 : 0 : fHaveGrant = true;
366 : : }
367 : :
368 : 0 : void Release() noexcept
369 : : {
370 [ # # ]: 0 : if (!fHaveGrant) {
371 : : return;
372 : : }
373 : 0 : sem->post();
374 : 0 : fHaveGrant = false;
375 : : }
376 : :
377 : 0 : bool TryAcquire() noexcept
378 : : {
379 [ # # # # ]: 0 : if (!fHaveGrant && sem->try_wait()) {
380 : 0 : fHaveGrant = true;
381 : : }
382 : 0 : return fHaveGrant;
383 : : }
384 : :
385 : : // Disallow copy.
386 : : CSemaphoreGrant(const CSemaphoreGrant&) = delete;
387 : : CSemaphoreGrant& operator=(const CSemaphoreGrant&) = delete;
388 : :
389 : : // Allow move.
390 : 0 : CSemaphoreGrant(CSemaphoreGrant&& other) noexcept
391 : 0 : {
392 : 0 : sem = other.sem;
393 : 0 : fHaveGrant = other.fHaveGrant;
394 : 0 : other.fHaveGrant = false;
395 [ # # ]: 0 : other.sem = nullptr;
396 : : }
397 : :
398 : 0 : CSemaphoreGrant& operator=(CSemaphoreGrant&& other) noexcept
399 : : {
400 : 0 : Release();
401 : 0 : sem = other.sem;
402 : 0 : fHaveGrant = other.fHaveGrant;
403 : 0 : other.fHaveGrant = false;
404 : 0 : other.sem = nullptr;
405 : 0 : return *this;
406 : : }
407 : :
408 [ # # # # ]: 0 : CSemaphoreGrant() noexcept : sem(nullptr), fHaveGrant(false) {}
[ # # ]
409 : :
410 : 0 : explicit CSemaphoreGrant(CSemaphore& sema, bool fTry = false) noexcept : sem(&sema), fHaveGrant(false)
411 : : {
412 : 0 : if (fTry) {
413 : 0 : TryAcquire();
414 : : } else {
415 : 0 : Acquire();
416 : : }
417 : : }
418 : :
419 : 0 : ~CSemaphoreGrant()
420 : : {
421 : 0 : Release();
422 : 0 : }
423 : :
424 : 0 : explicit operator bool() const noexcept
425 : : {
426 [ # # # # : 0 : return fHaveGrant;
# # ]
427 : : }
428 : : };
429 : :
430 : : #endif // BITCOIN_SYNC_H
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