[PATCH v5 5/8] perf record: Toggle overwrite ring buffer for reading

overwrite_evt_state is introduced to reflect the state of overwritable ring buffers. It is a state machine with 3 states: RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY ^ ^ | | |___(disallow)___/| ||

[PATCH v5 5/8] perf record: Toggle overwrite ring buffer for reading

overwrite_evt_state is introduced to reflect the state of overwritable ring buffers. It is a state machine with 3 states: RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY ^ ^ | | |___(disallow)___/| ||