Hi Cyrill,
On 11/10, Cyrill Gorcunov wrote:
>
> On Sun, Nov 09, 2025 at 06:15:33PM +0100, Oleg Nesterov wrote:
> ..
> > static int kill_sub_threads(struct task_struct *tsk)
> > {
> > struct signal_struct *sig = tsk->signal;
> > int err = -EINTR;
> >
> > read_lock(&tasklist_lock);
> > spin_lock_irq(&tsk->sighand->siglock);
> > if (!((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task)) {
> > sig->group_exec_task = tsk;
> > sig->notify_count = -zap_other_threads(tsk);
>
> Hi Oleg! I somehow manage to miss a moment -- why negative result here?
You know, initially I wrote
sig->notify_count = 0 - zap_other_threads(tsk);
to make it clear that this is not a typo ;)
This is for exit_notify() which does
/* mt-exec, de_thread() -> wait_for_notify_count() */
if (tsk->signal->notify_count < 0 && !++tsk->signal->notify_count)
wake_up_process(tsk->signal->group_exec_task);
Then setup_new_exec() sets notify_count > 0 for __exit_signal() which does
/* mt-exec, setup_new_exec() -> wait_for_notify_count() */
if (sig->notify_count > 0 && !--sig->notify_count)
wake_up_process(sig->group_exec_task);
Yes this needs more comments and (with or without this patch) cleanups.
Note that exit_notify() and __exit_signal() already (before this patch)
use ->notify_count almost the same way, just exit_notify() assumes that
notify_count < 0 means the !thread_group_leader() case in de_thread().
Oleg.
