diff options
Diffstat (limited to 'absl/synchronization')
| -rw-r--r-- | absl/synchronization/internal/waiter.cc | 7 | ||||
| -rw-r--r-- | absl/synchronization/internal/waiter.h | 11 |
2 files changed, 15 insertions, 3 deletions
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc index 8e7137705325..f1425872e5b6 100644 --- a/absl/synchronization/internal/waiter.cc +++ b/absl/synchronization/internal/waiter.cc @@ -342,8 +342,11 @@ bool Waiter::Wait(KernelTimeout t) { } void Waiter::Post() { - wakeups_.fetch_add(1, std::memory_order_release); // Post a wakeup. - Poke(); + // Post a wakeup. + if (wakeups_.fetch_add(1, std::memory_order_release) == 0) { + // We incremented from 0, need to wake a potential waiter. + Poke(); + } } void Waiter::Poke() { diff --git a/absl/synchronization/internal/waiter.h b/absl/synchronization/internal/waiter.h index cac81d5fd226..9540598be5d3 100644 --- a/absl/synchronization/internal/waiter.h +++ b/absl/synchronization/internal/waiter.h @@ -24,6 +24,10 @@ #include <pthread.h> #endif +#ifdef __linux__ +#include <linux/futex.h> +#endif + #ifdef ABSL_HAVE_SEMAPHORE_H #include <semaphore.h> #endif @@ -44,7 +48,12 @@ #define ABSL_WAITER_MODE ABSL_FORCE_WAITER_MODE #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 |