diff options
Diffstat (limited to 'absl/synchronization/blocking_counter.cc')
-rw-r--r-- | absl/synchronization/blocking_counter.cc | 40 |
1 files changed, 25 insertions, 15 deletions
diff --git a/absl/synchronization/blocking_counter.cc b/absl/synchronization/blocking_counter.cc index 3cea7aed..d2f82da3 100644 --- a/absl/synchronization/blocking_counter.cc +++ b/absl/synchronization/blocking_counter.cc @@ -14,41 +14,51 @@ #include "absl/synchronization/blocking_counter.h" +#include <atomic> + #include "absl/base/internal/raw_logging.h" namespace absl { ABSL_NAMESPACE_BEGIN -// Return whether int *arg is zero. -static bool IsZero(void *arg) { - return 0 == *reinterpret_cast<int *>(arg); +namespace { + +// Return whether int *arg is true. +bool IsDone(void *arg) { return *reinterpret_cast<bool *>(arg); } + +} // namespace + +BlockingCounter::BlockingCounter(int initial_count) + : count_(initial_count), + num_waiting_(0), + done_{initial_count == 0 ? true : false} { + ABSL_RAW_CHECK(initial_count >= 0, "BlockingCounter initial_count negative"); } bool BlockingCounter::DecrementCount() { - MutexLock l(&lock_); - count_--; - if (count_ < 0) { - ABSL_RAW_LOG( - FATAL, - "BlockingCounter::DecrementCount() called too many times. count=%d", - count_); + int count = count_.fetch_sub(1, std::memory_order_acq_rel) - 1; + ABSL_RAW_CHECK(count >= 0, + "BlockingCounter::DecrementCount() called too many times"); + if (count == 0) { + MutexLock l(&lock_); + done_ = true; + return true; } - return count_ == 0; + return false; } void BlockingCounter::Wait() { MutexLock l(&this->lock_); - ABSL_RAW_CHECK(count_ >= 0, "BlockingCounter underflow"); // only one thread may call Wait(). To support more than one thread, // implement a counter num_to_exit, like in the Barrier class. ABSL_RAW_CHECK(num_waiting_ == 0, "multiple threads called Wait()"); num_waiting_++; - this->lock_.Await(Condition(IsZero, &this->count_)); + this->lock_.Await(Condition(IsDone, &this->done_)); - // At this point, We know that all threads executing DecrementCount have - // released the lock, and so will not touch this object again. + // At this point, we know that all threads executing DecrementCount + // will not touch this object again. // Therefore, the thread calling this method is free to delete the object // after we return from this method. } |