diff options
Diffstat (limited to 'absl/synchronization/internal/waiter.h')
| -rw-r--r-- | absl/synchronization/internal/waiter.h | 64 |
1 files changed, 36 insertions, 28 deletions
diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h index 06032642..a6e6d4c7 100644 --- a/absl/synchronization/internal/waiter.h +++ b/absl/synchronization/internal/waiter.h @@ -18,10 +18,16 @@ #include "absl/base/config.h" -#ifndef _WIN32 +#ifdef _WIN32 +#include <sdkddkver.h> +#else #include <pthread.h> #endif +#ifdef __linux__ +#include <linux/futex.h> +#endif + #ifdef ABSL_HAVE_SEMAPHORE_H #include <semaphore.h> #endif @@ -40,9 +46,14 @@ #if defined(ABSL_FORCE_WAITER_MODE) #define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE -#elif defined(_WIN32) +#elif defined(_WIN32) && _WIN32_WINNT >= _WIN32_WINNT_VISTA #define ABSL_WAITER_MODE ABSL_WAITER_MODE_WIN32 -#elif defined(__linux__) +#elif defined(__BIONIC__) +// Bionic supports all the futex operations we need even when some of the futex +// definitions are missing. +#define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX +#elif defined(__linux__) && defined(FUTEX_CLOCK_REALTIME) +// FUTEX_CLOCK_REALTIME requires Linux >= 2.6.28. #define ABSL_WAITER_MODE ABSL_WAITER_MODE_FUTEX #elif defined(ABSL_HAVE_SEMAPHORE_H) #define ABSL_WAITER_MODE ABSL_WAITER_MODE_SEM @@ -51,20 +62,21 @@ #endif namespace absl { -inline namespace lts_2019_08_08 { +ABSL_NAMESPACE_BEGIN namespace synchronization_internal { // Waiter is an OS-specific semaphore. class Waiter { public: - // No constructor, instances use the reserved space in ThreadIdentity. - // All initialization logic belongs in `Init()`. - Waiter() = delete; + // Prepare any data to track waits. + Waiter(); + + // Not copyable or movable Waiter(const Waiter&) = delete; Waiter& operator=(const Waiter&) = delete; - // Prepare any data to track waits. - void Init(); + // Destroy any data to track waits. + ~Waiter(); // Blocks the calling thread until a matching call to `Post()` or // `t` has passed. Returns `true` if woken (`Post()` called), @@ -105,10 +117,13 @@ class Waiter { static_assert(sizeof(int32_t) == sizeof(futex_), "Wrong size for futex"); #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR + // REQUIRES: mu_ must be held. + void InternalCondVarPoke(); + pthread_mutex_t mu_; pthread_cond_t cv_; - std::atomic<int> waiter_count_; - std::atomic<int> wakeup_count_; // Unclaimed wakeups, written under lock. + int waiter_count_; + int wakeup_count_; // Unclaimed wakeups. #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_SEM sem_t sem_; @@ -118,26 +133,19 @@ class Waiter { std::atomic<int> wakeups_; #elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32 - // The Windows API has lots of choices for synchronization - // primivitives. We are using SRWLOCK and CONDITION_VARIABLE - // because they don't require a destructor to release system - // resources. - // - // However, we can't include Windows.h in our headers, so we use aligned - // storage buffers to define the storage. - using SRWLockStorage = - typename std::aligned_storage<sizeof(void*), alignof(void*)>::type; - using ConditionVariableStorage = - typename std::aligned_storage<sizeof(void*), alignof(void*)>::type; - // WinHelper - Used to define utilities for accessing the lock and // condition variable storage once the types are complete. class WinHelper; - SRWLockStorage mu_storage_; - ConditionVariableStorage cv_storage_; - std::atomic<int> waiter_count_; - std::atomic<int> wakeup_count_; + // REQUIRES: WinHelper::GetLock(this) must be held. + void InternalCondVarPoke(); + + // We can't include Windows.h in our headers, so we use aligned charachter + // buffers to define the storage of SRWLOCK and CONDITION_VARIABLE. + alignas(void*) unsigned char mu_storage_[sizeof(void*)]; + alignas(void*) unsigned char cv_storage_[sizeof(void*)]; + int waiter_count_; + int wakeup_count_; #else #error Unknown ABSL_WAITER_MODE @@ -145,7 +153,7 @@ class Waiter { }; } // namespace synchronization_internal -} // inline namespace lts_2019_08_08 +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_SYNCHRONIZATION_INTERNAL_WAITER_H_ |