diff options
Diffstat (limited to 'absl/synchronization/internal/waiter.cc')
-rw-r--r-- | absl/synchronization/internal/waiter.cc | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc index 96145780..d83d8087 100644 --- a/absl/synchronization/internal/waiter.cc +++ b/absl/synchronization/internal/waiter.cc @@ -129,6 +129,9 @@ void Waiter::Init() { bool Waiter::Wait(KernelTimeout t) { // Loop until we can atomically decrement futex from a positive // value, waiting on a futex while we believe it is zero. + // Note that, since the thread ticker is just reset, we don't need to check + // whether the thread is idle on the very first pass of the loop. + bool first_pass = true; while (true) { int32_t x = futex_.load(std::memory_order_relaxed); if (x != 0) { @@ -140,6 +143,8 @@ bool Waiter::Wait(KernelTimeout t) { return true; // Consumed a wakeup, we are done. } + + if (!first_pass) MaybeBecomeIdle(); const int err = Futex::WaitUntil(&futex_, 0, t); if (err != 0) { if (err == -EINTR || err == -EWOULDBLOCK) { @@ -150,8 +155,7 @@ bool Waiter::Wait(KernelTimeout t) { ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err); } } - - MaybeBecomeIdle(); + first_pass = false; } } @@ -219,6 +223,9 @@ bool Waiter::Wait(KernelTimeout t) { PthreadMutexHolder h(&mu_); waiter_count_.fetch_add(1, std::memory_order_relaxed); // Loop until we find a wakeup to consume or timeout. + // Note that, since the thread ticker is just reset, we don't need to check + // whether the thread is idle on the very first pass of the loop. + bool first_pass = true; while (true) { int x = wakeup_count_.load(std::memory_order_relaxed); if (x != 0) { @@ -232,6 +239,7 @@ bool Waiter::Wait(KernelTimeout t) { return true; } + if (!first_pass) MaybeBecomeIdle(); // No wakeups available, time to wait. if (!t.has_timeout()) { const int err = pthread_cond_wait(&cv_, &mu_); @@ -248,7 +256,7 @@ bool Waiter::Wait(KernelTimeout t) { ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err); } } - MaybeBecomeIdle(); + first_pass = false; } } @@ -288,6 +296,9 @@ bool Waiter::Wait(KernelTimeout t) { } // Loop until we timeout or consume a wakeup. + // Note that, since the thread ticker is just reset, we don't need to check + // whether the thread is idle on the very first pass of the loop. + bool first_pass = true; while (true) { int x = wakeups_.load(std::memory_order_relaxed); if (x != 0) { @@ -300,6 +311,7 @@ bool Waiter::Wait(KernelTimeout t) { return true; } + if (!first_pass) MaybeBecomeIdle(); // Nothing to consume, wait (looping on EINTR). while (true) { if (!t.has_timeout()) { @@ -313,7 +325,7 @@ bool Waiter::Wait(KernelTimeout t) { ABSL_RAW_LOG(FATAL, "sem_timedwait failed: %d", errno); } } - MaybeBecomeIdle(); + first_pass = false; } } @@ -401,6 +413,9 @@ bool Waiter::Wait(KernelTimeout t) { waiter_count_.fetch_add(1, std::memory_order_relaxed); // Loop until we find a wakeup to consume or timeout. + // Note that, since the thread ticker is just reset, we don't need to check + // whether the thread is idle on the very first pass of the loop. + bool first_pass = true; while (true) { int x = wakeup_count_.load(std::memory_order_relaxed); if (x != 0) { @@ -414,6 +429,7 @@ bool Waiter::Wait(KernelTimeout t) { return true; } + if (!first_pass) MaybeBecomeIdle(); // No wakeups available, time to wait. if (!SleepConditionVariableSRW(cv, mu, t.InMillisecondsFromNow(), 0)) { // GetLastError() returns a Win32 DWORD, but we assign to @@ -427,8 +443,7 @@ bool Waiter::Wait(KernelTimeout t) { ABSL_RAW_LOG(FATAL, "SleepConditionVariableSRW failed: %lu", err); } } - - MaybeBecomeIdle(); + first_pass = false; } } |