On Fri 02-10-15 21:33:08, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > Since T sends SIGKILL to all clone(CLONE_VM) tasks upon coredump, P needs
> > > to do
> >
> > It does that only to all threads in the _same_ thread group AFAIU.
>
> I'm confused. What the _same_ thread group?
>
> I can observe that SIGKILL is sent to all
>
> clone(CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)
> clone(CLONE_SIGHAND | CLONE_VM)
> clone(CLONE_VM)
I might be missing something crucial here but
copy_process has the following:
if (clone_flags & CLONE_THREAD) {
p->exit_signal = -1;
p->group_leader = current->group_leader;
p->tgid = current->tgid;
} else {
if (clone_flags & CLONE_PARENT)
p->exit_signal = current->group_leader->exit_signal;
else
p->exit_signal = (clone_flags & CSIGNAL);
p->group_leader = p;
p->tgid = p->pid;
}
So clone without CLONE_THREAD should create a new thread group leader
and so create a new thread group. Unless there is some other trickery
which I do not see right now for_each_thread from the parent task
shouldn't see those which are cloned without CLONE_THREAD.
[...]
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -295,6 +295,8 @@ static int zap_process(struct task_struct *start, int
> exit_code, int flags)
> for_each_thread(start, t) {
> task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
> if (t != current && t->mm) {
> + printk(KERN_INFO "Setting SIGKILL to %s(%u)\n",
> + t->comm, t->pid);
> sigaddset(&t->pending.signal, SIGKILL);
> signal_wake_up(t, 1);
> nr++;
> ---------- debug printk() patch end ----------
OK, but all your tasks should trigger SEGV. You cannot find out whether
all of them happened from the same zap_process, can you.
--
Michal Hocko
SUSE Labs
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