On 03/15, Josh Triplett wrote: > > On Sun, Mar 15, 2015 at 03:52:23PM +0100, Oleg Nesterov wrote: > > On 03/15, Josh Triplett wrote: > > > Add a CLONE_AUTOREAP flag to request this behavior unconditionally, > > > > Yes, CLONE_AUTOREAP is much better. And I agree (mostly) with that > > we should rely on do_notify_parent(). > > > > Howver the patch still doesn't look right. First of all, ->autoreap > > should be per-process, not per-thread. > > Ah, you're thinking of the case where the parent process launches a > ... Not really, although we probably need more sanity checks. It should be per-process simply because this "autoreap" affects the whole process. And the sub-threads are already "autoreap". And these 2 autoreap's semantics differ, we should not confuse them. > (As an aside, what *is* the use case for CLONE_PARENT without > CLONE_THREAD?) To me CLONE_PARENT is another historical mistake and the source of misc problems ;) > > And there are ptrace/mt issues, > > it seems. Just for example, we should avoid EXIT_TRACE if autoreap in > > wait_task_zombie() even if we are going to re-notify parent. > > I don't see how EXIT_TRACE can happen in wait_task_zombie if autoreap is > set. wait_task_zombie does a cmpxchg with exit_state and doesn't > proceed unless exit_state was EXIT_ZOMBIE, and I don't see how we can > ever reach the EXIT_ZOMBIE state if autoreap. Because you again forgot about ptrace ;) Josh. Let me try to summarise this later when I have time. Again, I am not sure, perhaps this is even simpler than I currently think. And let me apologize in advance, most probably I will be busy tomorrow. > > EXCEPT: do we really want SIGCHLD from the exiting child? I think we > > do not. I won't really argue though, but this should be discussed and > > documented. IIUC, with your patch it is still sent. > > I think we do, yes. The caller of clone can already specify what signal > they want, including no signal at all. If they specify a signal > (SIGCHLD or otherwise) along with CLONE_AUTOREAP, we can send that > signal. OK. Agreed. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
