列出当前进程中的所有线程？

问题描述：

我试图执行一个系统调用，让我得到的线程数当前进程。我是新来的Linux内核，所以我对它的理解是有限的。

I'm trying to implement a syscall which allows me to get the number of threads for the current process. I am new to the linux kernel, and so my understanding of it is limited.

目前，我正尝试通过所有的task_structs迭代，他们的线程组领导的PID比作电流线程组领导的PID：

Currently, I am trying to iterate through all the task_structs, and compare their threadgroup leader's pid to the current threadgroup leader's pid:

// ...
int nthreads = 0;
struct task_struct *task_it;
for_each_process(task_it) {
    if (task_it->group_leader->pid == current->group_leader->pid) {
        nthreads++;
    }
}
// ...

不过，这似乎并不奏效（快速测试一些产卵的pthreads仍给 1 有关group_leader什么是共同在同一的所有线程流程？

However, this doesn't seem to be working (a quick test spawning some pthreads is still giving 1. What about the group_leader is common to all threads in the same process?

答

与code的问题是什么内核调用PID（即 PID 字段的的task_struct ）是用户空间调用TID（即它是什么由 sys_gettid返回（），是每个线程唯一）。什么用户空间调用PID被称为TGID在内核（即工作组ID） - 这是什么 sys_getpid（）系统调用返回

The problem with your code is that what the kernel calls a PID (the pid field of task_struct) is what userspace calls a TID (ie. it's what's returned by sys_gettid() and is unique per thread). What userspace calls a PID is called a TGID in the kernel (for "task group ID") - that's what the sys_getpid() syscall returns.

您不必实际检查TGID，虽然 - 只是比较结构的task_struct * 指针就足够了：

You don't need to actually check the TGID, though - just comparing the struct task_struct * pointers is enough:

if (task_it->group_leader == current->group_leader) {

顺便说一句，你可以只遍历了的 thread_group 名单电流是的成员（含 while_each_thread（）），那么你就不需要任何测试的。甚至更好，只需要使用 get_nr_threads（电流）。

By the way, you could just iterate over the thread_group list that current is a member of (with while_each_thread()), then you wouldn't need any test at all. Or even better, just use get_nr_threads(current).

注意，遍历所有的任务列表需要被包裹在所有方法rcu_read_lock（）; / rcu_read_unlock（）; 是正确的。

Note that all methods that loop over the task lists need to be wrapped in rcu_read_lock(); / rcu_read_unlock(); to be correct.

列出当前进程中的所有线程？

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