マルチスレッディング (pthreads(7) 参照)

pthread_getcpuclockid() 関数はスレッドセーフである。

プログラムのソース

/* "-lrt" でリンクする */
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include <errno.h>
#define handle_error(msg) \


        do { perror(msg); exit(EXIT_FAILURE); } while (0)
#define handle_error_en(en, msg) \


        do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
static void *
thread_start(void *arg)
{


    printf("Subthread starting infinite loop\n");


    for (;;)


        continue;
}
static void
pclock(char *msg, clockid_t cid)
{


    struct timespec ts;


    printf("%s", msg);


    if (clock_gettime(cid, &ts) == -1)


        handle_error("clock_gettime");


    printf("%4ld.%03ld\n", ts.tv_sec, ts.tv_nsec / 1000000);
}
int
main(int argc, char *argv[])
{


    pthread_t thread;


    clockid_t cid;


    int j, s;


    s = pthread_create(&thread, NULL, thread_start, NULL);


    if (s != 0)


        handle_error_en(s, "pthread_create");


    printf("Main thread sleeping\n");


    sleep(1);


    printf("Main thread consuming some CPU time...\n");


    for (j = 0; j < 2000000; j++)


        getppid();


    pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);


    s = pthread_getcpuclockid(pthread_self(), &cid);


    if (s != 0)


        handle_error_en(s, "pthread_getcpuclockid");


    pclock("Main thread CPU time:   ", cid);


    /* The preceding 4 lines of code could have been replaced by:


       pclock("Main thread CPU time:   ", CLOCK_THREAD_CPUTIME_ID); */


    s = pthread_getcpuclockid(thread, &cid);


    if (s != 0)


        handle_error_en(s, "pthread_getcpuclockid");


    pclock("Subthread CPU time: 1    ", cid);


    exit(EXIT_SUCCESS);         /* Terminates both threads */
}