diff --git a/m-core.h b/m-core.h index f2463c11..9989ed3a 100644 --- a/m-core.h +++ b/m-core.h @@ -2371,4 +2371,54 @@ m_core_hash (const void *str, size_t length) } } while (0) #endif +/************************************************************/ +/******************* Exponential Backoff ********************/ +/************************************************************/ + +#ifndef M_BACKOFF_MAX_COUNT +#define M_BACKOFF_MAX_COUNT 6 +#endif + +typedef struct m_backoff_s { + unsigned int count; + unsigned int seed; +} m_backoff_t[1]; + +static inline void +m_backoff_init(m_backoff_t backoff) +{ + backoff->count = 0; + backoff->seed = rand(); +} + +static inline void +m_backoff_reset(m_backoff_t backoff) +{ + backoff->count = 0; +} + +static inline void +m_backoff_wait(m_backoff_t backoff) +{ + volatile int x = 0; + /* Cheap but fast pseudo random */ + backoff->seed = backoff->seed * 34721 + 17449; + const unsigned int mask = (1U << backoff->count) -1; + const unsigned int count = mask & (backoff->seed >> 8); + /* Active sleep */ + for(unsigned int i = 0; i <= count; i++) + x = 0; + (void) x; + /* Increment count for next step if needed */ + backoff->count += (backoff->count < M_BACKOFF_MAX_COUNT); +} + +static inline void +m_backoff_clear(m_backoff_t backoff) +{ + // Nothing to do + (void) backoff; +} + + #endif