请问linux下线程和一个定时器之间同步的问题！

#include <stdio.h>
#include <pthread.h>

#include <sys/time.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
//#define BUFFER_SIZE 16
#define BUFFER_SIZE 2
#define OVER ( - 1)

struct prodcons
{
    int buffer[BUFFER_SIZE];
    pthread_mutex_t lock;
    int readpos, writepos;
    pthread_cond_t notempty;
    pthread_cond_t notfull;
};
struct prodcons buffer;

void init(struct prodcons *b)
{
    pthread_mutex_init(&b->lock, NULL);
    pthread_cond_init(&b->notempty, NULL);
    pthread_cond_init(&b->notfull, NULL);
    b->readpos = 0;
    b->writepos = 0;
}

void put(struct prodcons *b, int data)
{
    pthread_mutex_lock(&b->lock);

    if ((b->writepos + 1) % BUFFER_SIZE == b->readpos)
    {
        pthread_cond_wait(&b->notfull, &b->lock);
    }

    b->buffer[b->writepos] = data;
    b->writepos++;
    if (b->writepos >= BUFFER_SIZE)
        b->writepos =