gettid 和pthread_self的区别

最新推荐文章于 2024-10-19 21:07:07 发布

转载最新推荐文章于 2024-10-19 21:07:07 发布 · 1.4k 阅读

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#thread #struct #numbers #linux #null #join

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本文探讨了Linux中gettid系统调用与pthread_self函数的区别，解析了它们各自返回的线程ID类型，并通过示例代码展示了如何使用这两种方法获取线程ID。

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; }