gettid 和pthread_self的区别

gettid 和pthread_self的区别

The man page for gettid says:


The thread ID returned by this call is not the same thing as a POSIX thread ID
(i.e., the opaque value returned by pthread_self(3)).

看来，线程的id，在linux中分为POSIX thread ID , 和内核中对每一个线程的id.

gettid是linux 的一个系统调用， 查看sys_gettid
/* Thread ID - the internal kernel "pid" */
asmlinkage long sys_gettid(void)
{
    return task_pid_vnr(current);
}


struct upid {
    /* Try to keep pid_chain in the same cacheline as nr for find_pid */
    int nr;
    struct pid_namespace *ns;
    struct hlist_node pid_chain;
};

struct pid
{
    atomic_t count;
    /* lists of tasks that use this pid */
    struct hlist_head tasks[PIDTYPE_MAX];
    struct rcu_head rcu;
    int level;
    struct upid numbers[1];
};


这里面的level不清楚是什么含义？ 有知道的告诉我，多谢了。




问：_syscall[0-6]跑哪里去了
答：没有了

问：那现在用啥呢？
答：用系统调用 syscall(2)，第一个参数是SYS_name，后面参数照写







 

#define _GNU_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/unistd.h>
#include <sys/syscall.h>

void *thsf(void *arg)
{
    pthread_t th;
    char *retstr;
    retstr=malloc(50);
    memset(retstr,0,50);


    strcpy(retstr,"New thread quit!");


    th=pthread_self();
#if 1
    printf("New thread,pid:%d,tid:%x,another tid:%x.\n",
                      getpid(),
                      th,
                      (long)syscall(SYS_gettid));
#endif
   
    pthread_exit(retstr);
}

int main()
{
        pthread_t nth1,mth,oth;
        void *a;
        if(pthread_create(&nth1,NULL,thsf,NULL))
                printf("Error create new thread.\n");
        mth=pthread_self();

        printf("Main thread,pid:%d,tid:%x,another tid:%x.\n",getpid(),mth,(long)syscall(SYS_gettid));
        if(!pthread_join(nth1,&a))
        {
                printf("New thread quit,message from new thread:%s.\n",(char *)a);
                free((char *)a);
        }
        return 0;
}