dturvene

/* 
 * lock_t - type for the spinlock bit array
 * C11 spec says to use an atomic for atomic lock value
 */
typedef atomic_uint lock_t;

/**
 * lockholder - bit array marking the thread holding the spinlock
 *
 * This will be 0 if no thread holds lock, otherwise ONE of the defined lock

dturvene

/**
 * event types to log
 */
typedef enum evtid {
	EVT_ENQ = 1,
	EVT_DEQ = 2,
	EVT_DEQ_IDLE = 3,
	EVT_END = 4,
} evtid_t;

dturvene

/**
 * q_consumer: pthread to call q_deq
 * @arg: pthread arguments passed from pthread_create (not used)
 *
 * This pthread loops until the END_EL value is received. It trys to dequeue a
 * value. If one is available the function logs it, otherwise it increases and
 * idle counter. After a value is dequeued it will also log the idle counter.
 * 
 * When the consumer thread starts before the producer it busy-waits
 * until the first value is written by the producer.

dturvene

/**
 * q_deq: dequeue the oldest ringbuffer element
 * @sqp: the simple queue context structure
 * @valp: return the value in the current deq element
 *
 * Logic:
 * - If no valid elements, return -1
 * - get value from bufs element
 * - mark queue element as invalid (for debugging) and decrement counter
 * - if last element then wrap to first, otherwise move to next element

dturvene

/* Fixed size of the array used for queuing */
#define QDEPTH 4096

/**
 * struct sq - simple queue
 * @bufs: fix array of buffers
 * @enq: pointer to the bufs element to fill for the newest value,
 *       the element will either be invalid or, if valid, the
 *       oldest filled.
 * @deq: pointer to the bufs element to drain next,

dturvene

/**
 * q_enq: enqueue a new value into the oldest ringbuffer element
 * @sqp: the simple queue context structure
 * @val: value to enter into current bufs element
 *
 * Logic:
 * - update element value and wrap or increment enq pointer
 * - if all bufs are being used then move the deq pointer to the
 *   current oldest (one more than the newest!), 
 *   if bufs still available then increment buf count