Re: [PATCH v4] kernel/signal: Signal-based pre-coredump notification

[Enke Chen]

Hi, Oleg:

Yes, it should be the "real_parent" that is more interested in the notification.
Will revert back.

+static void do_notify_parent_predump(void)
+{
+	struct task_struct *parent;
+	int sig;
+
+	rcu_read_lock();
+	parent = rcu_dereference(current->real_parent);
+	sig = parent->signal->predump_signal;
+	if (sig != 0)
+		do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID);
+	rcu_read_unlock();
+}

Thanks.  -- Enke

On 10/29/18 4:18 AM, Oleg Nesterov wrote:
> Hi,
> 
> On 10/26, Enke Chen wrote:
>>
>> This is really a good idea given that "parent" is declared as RCU-protected.
>> Just a bit odd, though, that the "parent" has not been accessed this way in
>> the code base.
> 
> It is acccessed when possible,
> 
>> So just to confirm: the revised code would look like the following:
>>
>> static void do_notify_parent_predump(void)
>> {
>>         struct task_struct *parent;
>>         int sig;
>>
>>         rcu_read_lock();
>>         parent = rcu_dereference(current->parent);
>>         sig = parent->signal->predump_signal;
>>         if (sig != 0)
>>                 do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID);
>>         rcu_read_unlock();
>> }
> 
> Yes, this is what I meant.
> 
> But I still think do_notify_parent_predump() should notify ->real_parent,
> not ->parent.
> 
> Oleg.
>