Oleg Nesterov wrote:
On 08/24, Pavel Emelyanov wrote:
The major differences of creating a new thread from creating a
new process is that
1. newbie's tgid is set to leader's
2. newbie's leader is set to leader
3. newbie is added to leader's thread_list
(Surely, the are many other major differences, but from the pids virtualization
POV - yes ;)
+static void setup_new_thread(struct task_struct *thr, struct task_struct
*leader)
+{
+ thr->tgid = leader->tgid;
+ thr->group_leader = leader;
+ list_add_tail_rcu(&thr->thread_group, &leader->thread_group);
+}
Imho, this name is a bit "too generic". Not that I can suggest something
better... copy_sub_thread/copy_group_leader ?
@@ -1147,9 +1161,6 @@ static struct task_struct *copy_process(
}
p->pid = pid_nr(pid);
- p->tgid = p->pid;
- if (clone_flags & CLONE_THREAD)
- p->tgid = current->tgid;
I agree, it is absoulutely not clear why should we set ->tgid here, and it
would be nice to consolidate "if (CLONE_THREAD)" checks, but do we really
need the helpers above? There are very simple, and have the only one caller.
Sometimes it is good to see what's going on without pressing C-]
Not that I against this patch, just I'm not sure it really simplifies things.
Perhaps I missed something else you have in mind.
Me too, but while cleaning up the pid_t usage over the kernel I found
this place to be one of the most difficult from "how to make it better"
point of view. We need to hide the pid/tgid explicit usage somehow, but
the problem is that pid and tgid are set in this place and de_thread()
only and making helpers like set_task_tgid() doesn't sound reasonable.
Oleg.
Thanks,
Pavel
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