diff options
| -rw-r--r-- | absl/base/call_once.h | 11 | ||||
| -rw-r--r-- | absl/base/internal/spinlock.h | 5 | ||||
| -rw-r--r-- | absl/base/internal/spinlock_wait.h | 12 | ||||
| -rw-r--r-- | absl/status/status.h | 1 |
4 files changed, 9 insertions, 20 deletions
diff --git a/absl/base/call_once.h b/absl/base/call_once.h index 5b468af8..96109f53 100644 --- a/absl/base/call_once.h +++ b/absl/base/call_once.h @@ -177,15 +177,8 @@ void CallOnceImpl(std::atomic<uint32_t>* control, scheduling_mode) == kOnceInit) { base_internal::invoke(std::forward<Callable>(fn), std::forward<Args>(args)...); - // The call to SpinLockWake below is an optimization, because the waiter - // in SpinLockWait is waiting with a short timeout. The atomic load/store - // sequence is slightly faster than an atomic exchange: - // old_control = control->exchange(base_internal::kOnceDone, - // std::memory_order_release); - // We opt for a slightly faster case when there are no waiters, in spite - // of longer tail latency when there are waiters. - old_control = control->load(std::memory_order_relaxed); - control->store(base_internal::kOnceDone, std::memory_order_release); + old_control = + control->exchange(base_internal::kOnceDone, std::memory_order_release); if (old_control == base_internal::kOnceWaiter) { base_internal::SpinLockWake(control, true); } diff --git a/absl/base/internal/spinlock.h b/absl/base/internal/spinlock.h index e6ac9e64..dce1c854 100644 --- a/absl/base/internal/spinlock.h +++ b/absl/base/internal/spinlock.h @@ -15,11 +15,8 @@ // // Most users requiring mutual exclusion should use Mutex. -// SpinLock is provided for use in three situations: +// SpinLock is provided for use in two situations: // - for use in code that Mutex itself depends on -// - to get a faster fast-path release under low contention (without an -// atomic read-modify-write) In return, SpinLock has worse behaviour under -// contention, which is why Mutex is preferred in most situations. // - for async signal safety (see below) // SpinLock is async signal safe. If a spinlock is used within a signal diff --git a/absl/base/internal/spinlock_wait.h b/absl/base/internal/spinlock_wait.h index 169bc749..c34ce41c 100644 --- a/absl/base/internal/spinlock_wait.h +++ b/absl/base/internal/spinlock_wait.h @@ -43,18 +43,16 @@ uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n, const SpinLockWaitTransition trans[], SchedulingMode scheduling_mode); -// If possible, wake some thread that has called SpinLockDelay(w, ...). If -// "all" is true, wake all such threads. This call is a hint, and on some -// systems it may be a no-op; threads calling SpinLockDelay() will always wake -// eventually even if SpinLockWake() is never called. +// If possible, wake some thread that has called SpinLockDelay(w, ...). If `all` +// is true, wake all such threads. On some systems, this may be a no-op; on +// those systems, threads calling SpinLockDelay() will always wake eventually +// even if SpinLockWake() is never called. void SpinLockWake(std::atomic<uint32_t> *w, bool all); // Wait for an appropriate spin delay on iteration "loop" of a // spin loop on location *w, whose previously observed value was "value". // SpinLockDelay() may do nothing, may yield the CPU, may sleep a clock tick, -// or may wait for a delay that can be truncated by a call to SpinLockWake(w). -// In all cases, it must return in bounded time even if SpinLockWake() is not -// called. +// or may wait for a call to SpinLockWake(w). void SpinLockDelay(std::atomic<uint32_t> *w, uint32_t value, int loop, base_internal::SchedulingMode scheduling_mode); diff --git a/absl/status/status.h b/absl/status/status.h index c4d6fce0..9019e6c2 100644 --- a/absl/status/status.h +++ b/absl/status/status.h @@ -57,6 +57,7 @@ #include "absl/container/inlined_vector.h" #include "absl/status/internal/status_internal.h" #include "absl/strings/cord.h" +#include "absl/strings/string_view.h" #include "absl/types/optional.h" namespace absl { |