#include"pthread_impl.h"#include <threads.h>intmtx_lock(mtx_t *m){if(m->_m_type == PTHREAD_MUTEX_NORMAL && !a_cas(&m->_m_lock,0, EBUSY))return thrd_success;/* Calling mtx_timedlock with a null pointer is an extension. * It is convenient, here to avoid duplication of the logic * for return values. */returnmtx_timedlock(m,0);}