diff options
Diffstat (limited to 'absl/synchronization/mutex.h')
| -rw-r--r-- | absl/synchronization/mutex.h | 141 |
1 files changed, 79 insertions, 62 deletions
diff --git a/absl/synchronization/mutex.h b/absl/synchronization/mutex.h index 52401fe3..f49e0c83 100644 --- a/absl/synchronization/mutex.h +++ b/absl/synchronization/mutex.h @@ -31,22 +31,23 @@ // // MutexLock - An RAII wrapper to acquire and release a `Mutex` for exclusive/ // write access within the current scope. +// // ReaderMutexLock // - An RAII wrapper to acquire and release a `Mutex` for shared/read // access within the current scope. // // WriterMutexLock -// - Alias for `MutexLock` above, designed for use in distinguishing -// reader and writer locks within code. +// - Effectively an alias for `MutexLock` above, designed for use in +// distinguishing reader and writer locks within code. // // In addition to simple mutex locks, this file also defines ways to perform // locking under certain conditions. // -// Condition - (Preferred) Used to wait for a particular predicate that -// depends on state protected by the `Mutex` to become true. -// CondVar - A lower-level variant of `Condition` that relies on -// application code to explicitly signal the `CondVar` when -// a condition has been met. +// Condition - (Preferred) Used to wait for a particular predicate that +// depends on state protected by the `Mutex` to become true. +// CondVar - A lower-level variant of `Condition` that relies on +// application code to explicitly signal the `CondVar` when +// a condition has been met. // // See below for more information on using `Condition` or `CondVar`. // @@ -72,15 +73,6 @@ #include "absl/synchronization/internal/per_thread_sem.h" #include "absl/time/time.h" -// Decide if we should use the non-production implementation because -// the production implementation hasn't been fully ported yet. -#ifdef ABSL_INTERNAL_USE_NONPROD_MUTEX -#error ABSL_INTERNAL_USE_NONPROD_MUTEX cannot be directly set -#elif defined(ABSL_LOW_LEVEL_ALLOC_MISSING) -#define ABSL_INTERNAL_USE_NONPROD_MUTEX 1 -#include "absl/synchronization/internal/mutex_nonprod.inc" -#endif - namespace absl { ABSL_NAMESPACE_BEGIN @@ -155,7 +147,7 @@ class ABSL_LOCKABLE Mutex { // // Example usage: // namespace foo { - // ABSL_CONST_INIT Mutex mu(absl::kConstInit); + // ABSL_CONST_INIT absl::Mutex mu(absl::kConstInit); // } explicit constexpr Mutex(absl::ConstInitType); @@ -170,7 +162,7 @@ class ABSL_LOCKABLE Mutex { // Mutex::Unlock() // // Releases this `Mutex` and returns it from the exclusive/write state to the - // free state. Caller must hold the `Mutex` exclusively. + // free state. Calling thread must hold the `Mutex` exclusively. void Unlock() ABSL_UNLOCK_FUNCTION(); // Mutex::TryLock() @@ -461,24 +453,13 @@ class ABSL_LOCKABLE Mutex { static void InternalAttemptToUseMutexInFatalSignalHandler(); private: -#ifdef ABSL_INTERNAL_USE_NONPROD_MUTEX - friend class CondVar; - - synchronization_internal::MutexImpl *impl() { return impl_.get(); } - - synchronization_internal::SynchronizationStorage< - synchronization_internal::MutexImpl> - impl_; -#else std::atomic<intptr_t> mu_; // The Mutex state. // Post()/Wait() versus associated PerThreadSem; in class for required // friendship with PerThreadSem. - static inline void IncrementSynchSem(Mutex *mu, - base_internal::PerThreadSynch *w); - static inline bool DecrementSynchSem( - Mutex *mu, base_internal::PerThreadSynch *w, - synchronization_internal::KernelTimeout t); + static void IncrementSynchSem(Mutex *mu, base_internal::PerThreadSynch *w); + static bool DecrementSynchSem(Mutex *mu, base_internal::PerThreadSynch *w, + synchronization_internal::KernelTimeout t); // slow path acquire void LockSlowLoop(SynchWaitParams *waitp, int flags); @@ -504,7 +485,6 @@ class ABSL_LOCKABLE Mutex { void Trans(MuHow how); // used for CondVar->Mutex transfer void Fer( base_internal::PerThreadSynch *w); // used for CondVar->Mutex transfer -#endif // Catch the error of writing Mutex when intending MutexLock. Mutex(const volatile Mutex * /*ignored*/) {} // NOLINT(runtime/explicit) @@ -525,22 +505,36 @@ class ABSL_LOCKABLE Mutex { // Example: // // Class Foo { -// +// public: // Foo::Bar* Baz() { -// MutexLock l(&lock_); +// MutexLock lock(&mu_); // ... // return bar; // } // // private: -// Mutex lock_; +// Mutex mu_; // }; class ABSL_SCOPED_LOCKABLE MutexLock { public: + // Constructors + + // Calls `mu->Lock()` and returns when that call returns. That is, `*mu` is + // guaranteed to be locked when this object is constructed. Requires that + // `mu` be dereferenceable. explicit MutexLock(Mutex *mu) ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) : mu_(mu) { this->mu_->Lock(); } + // Like above, but calls `mu->LockWhen(cond)` instead. That is, in addition to + // the above, the condition given by `cond` is also guaranteed to hold when + // this object is constructed. + explicit MutexLock(Mutex *mu, const Condition &cond) + ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) + : mu_(mu) { + this->mu_->LockWhen(cond); + } + MutexLock(const MutexLock &) = delete; // NOLINT(runtime/mutex) MutexLock(MutexLock&&) = delete; // NOLINT(runtime/mutex) MutexLock& operator=(const MutexLock&) = delete; @@ -562,6 +556,12 @@ class ABSL_SCOPED_LOCKABLE ReaderMutexLock { mu->ReaderLock(); } + explicit ReaderMutexLock(Mutex *mu, const Condition &cond) + ABSL_SHARED_LOCK_FUNCTION(mu) + : mu_(mu) { + mu->ReaderLockWhen(cond); + } + ReaderMutexLock(const ReaderMutexLock&) = delete; ReaderMutexLock(ReaderMutexLock&&) = delete; ReaderMutexLock& operator=(const ReaderMutexLock&) = delete; @@ -584,6 +584,12 @@ class ABSL_SCOPED_LOCKABLE WriterMutexLock { mu->WriterLock(); } + explicit WriterMutexLock(Mutex *mu, const Condition &cond) + ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) + : mu_(mu) { + mu->WriterLockWhen(cond); + } + WriterMutexLock(const WriterMutexLock&) = delete; WriterMutexLock(WriterMutexLock&&) = delete; WriterMutexLock& operator=(const WriterMutexLock&) = delete; @@ -622,16 +628,26 @@ class ABSL_SCOPED_LOCKABLE WriterMutexLock { // `noexcept`; until then this requirement cannot be enforced in the // type system.) // -// Note: to use a `Condition`, you need only construct it and pass it within the -// appropriate `Mutex' member function, such as `Mutex::Await()`. +// Note: to use a `Condition`, you need only construct it and pass it to a +// suitable `Mutex' member function, such as `Mutex::Await()`, or to the +// constructor of one of the scope guard classes. // -// Example: +// Example using LockWhen/Unlock: // // // assume count_ is not internal reference count // int count_ ABSL_GUARDED_BY(mu_); +// Condition count_is_zero(+[](int *count) { return *count == 0; }, &count_); +// +// mu_.LockWhen(count_is_zero); +// // ... +// mu_.Unlock(); // -// mu_.LockWhen(Condition(+[](int* count) { return *count == 0; }, -// &count_)); +// Example using a scope guard: +// +// { +// MutexLock lock(&mu_, count_is_zero); +// // ... +// } // // When multiple threads are waiting on exactly the same condition, make sure // that they are constructed with the same parameters (same pointer to function @@ -686,10 +702,10 @@ class Condition { // }; // mu_.Await(Condition(&reached)); // - // NOTE: never use "mu_.AssertHeld()" instead of "mu_.AssertReadHeld()" in the - // lambda as it may be called when the mutex is being unlocked from a scope - // holding only a reader lock, which will make the assertion not fulfilled and - // crash the binary. + // NOTE: never use "mu_.AssertHeld()" instead of "mu_.AssertReaderHeld()" in + // the lambda as it may be called when the mutex is being unlocked from a + // scope holding only a reader lock, which will make the assertion not + // fulfilled and crash the binary. // See class comment for performance advice. In particular, if there // might be more than one waiter for the same condition, make sure @@ -838,17 +854,10 @@ class CondVar { void EnableDebugLog(const char *name); private: -#ifdef ABSL_INTERNAL_USE_NONPROD_MUTEX - synchronization_internal::CondVarImpl *impl() { return impl_.get(); } - synchronization_internal::SynchronizationStorage< - synchronization_internal::CondVarImpl> - impl_; -#else bool WaitCommon(Mutex *mutex, synchronization_internal::KernelTimeout t); void Remove(base_internal::PerThreadSynch *s); void Wakeup(base_internal::PerThreadSynch *w); std::atomic<intptr_t> cv_; // Condition variable state. -#endif CondVar(const CondVar&) = delete; CondVar& operator=(const CondVar&) = delete; }; @@ -870,6 +879,15 @@ class ABSL_SCOPED_LOCKABLE MutexLockMaybe { this->mu_->Lock(); } } + + explicit MutexLockMaybe(Mutex *mu, const Condition &cond) + ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) + : mu_(mu) { + if (this->mu_ != nullptr) { + this->mu_->LockWhen(cond); + } + } + ~MutexLockMaybe() ABSL_UNLOCK_FUNCTION() { if (this->mu_ != nullptr) { this->mu_->Unlock(); } } @@ -892,6 +910,13 @@ class ABSL_SCOPED_LOCKABLE ReleasableMutexLock { : mu_(mu) { this->mu_->Lock(); } + + explicit ReleasableMutexLock(Mutex *mu, const Condition &cond) + ABSL_EXCLUSIVE_LOCK_FUNCTION(mu) + : mu_(mu) { + this->mu_->LockWhen(cond); + } + ~ReleasableMutexLock() ABSL_UNLOCK_FUNCTION() { if (this->mu_ != nullptr) { this->mu_->Unlock(); } } @@ -906,12 +931,6 @@ class ABSL_SCOPED_LOCKABLE ReleasableMutexLock { ReleasableMutexLock& operator=(ReleasableMutexLock&&) = delete; }; -#ifdef ABSL_INTERNAL_USE_NONPROD_MUTEX - -inline constexpr Mutex::Mutex(absl::ConstInitType) : impl_(absl::kConstInit) {} - -#else - inline Mutex::Mutex() : mu_(0) { ABSL_TSAN_MUTEX_CREATE(this, __tsan_mutex_not_static); } @@ -920,8 +939,6 @@ inline constexpr Mutex::Mutex(absl::ConstInitType) : mu_(0) {} inline CondVar::CondVar() : cv_(0) {} -#endif // ABSL_INTERNAL_USE_NONPROD_MUTEX - // static template <typename T> bool Condition::CastAndCallMethod(const Condition *c) { @@ -988,7 +1005,7 @@ void RegisterMutexProfiler(void (*fn)(int64_t wait_timestamp)); // // This has the same memory ordering concerns as RegisterMutexProfiler() above. void RegisterMutexTracer(void (*fn)(const char *msg, const void *obj, - int64_t wait_cycles)); + int64_t wait_cycles)); // TODO(gfalcon): Combine RegisterMutexProfiler() and RegisterMutexTracer() // into a single interface, since they are only ever called in pairs. @@ -1059,7 +1076,7 @@ ABSL_NAMESPACE_END // By changing our extension points to be extern "C", we dodge this // check. extern "C" { -void AbslInternalMutexYield(); +void ABSL_INTERNAL_C_SYMBOL(AbslInternalMutexYield)(); } // extern "C" #endif // ABSL_SYNCHRONIZATION_MUTEX_H_ |