Defined in carb/thread/Util.h

template<size_t PausesBeforeYield = 16>
class AtomicBackoff

A utility class for providing a growing number of pause instructions, followed by yielding.

The pause instruction is effectively CARB_HARDWARE_PAUSE().

Very fast to construct, often used in a loop such as:

for (AtomicBackoff<> b;; b.pause())
    if (condition())

Template Parameters

PausesBeforeYield – the number of pauses that will occur before yielding begins. See AtomicBackoff::pause().

Public Functions

constexpr AtomicBackoff() noexcept = default


inline void reset() noexcept

Resets *this.

inline void pause() noexcept

Every time called, will pause for exponentially longer, and after a certain amount will instead yield.

Pause is as via CARB_HARDWARE_PAUSE. Yield is as via std::this_thread::yield(). The pause count starts at 1 when reset() or newly constructed. Each time this function is called, the CPU pause instruction is executed count times and count is doubled. If called when count exceeds kPausesBeforeYield, a yield occurs instead. Calling reset() resets the count to 1.

inline bool pauseWithoutYield() noexcept

Similar to pause() but if would yield, instead returns false.


true if the internal count is less than kPausesBeforeYield; false otherwise.

Public Static Functions

static inline void pauseLoop(size_t count) noexcept

A helper function for executing the CPU pause instruction count times.


count – The number of times to execute CARB_HARDWARE_PAUSE().

Public Static Attributes

static constexpr size_t kPausesBeforeYield = PausesBeforeYield

The number of pauses that should be executed before yielding the thread.