Messages in this thread | | | Date | Thu, 12 Jul 2018 15:42:20 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC][PATCH 11/11] signal: Ignore all but multi-process signals that come in during fork. |
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On 07/11, Eric W. Biederman wrote: > > Oleg Nesterov <oleg@redhat.com> writes: > > >> - recalc_sigpending(); > >> - if (signal_pending(current)) { > >> + if (read_seqcount_retry(¤t->signal->multi_process_seq, seq) || > >> + fatal_signal_pending(current)) { > >> retval = -ERESTARTNOINTR; > >> goto bad_fork_cancel_cgroup; > > > > So once again, I think this is not right, see the discussion on > > bugzilla. > > I am trying to dig through and understand your concerns. I am having > difficulty understanding your concerns. > > Do the previous patches look good to you?
Yes, yes, personally I like 1-10 after a quick glance. I'll try to read this series carefully later, but I don't think I will find something really wrong.
> If I understand you correctly. Your concern is that since we added the: > > recalc_sigpending(); > if (signal_pending(current)) > return -ERESTARTNOINTR; > > Other (non-signal) code such as the freezer has come to depend upon that > test. Changing the test in the proposed way will allow the new child to > escape the freezer, as it is not guaranteed the new child will be > frozen.
Yes.
> > It seems reasonable to look at other things that set TIF_SIGPENDING and > see if any of them are broken by the fork changes.
Again, please look at do_signal_stop(). If it was the source of signal_pending(), copy_process() should fail. Or we should update the new thread to participate in group-stop, but then we need to set TIF_SIGPENDING, copy the relevant part of current->jobctl, and increment ->group_stop_count at least.
> A practical (and fixable) problem with your patch was that you modified > task->blocked which was then copied to the child. So all children now > would start with all signals being blocked.
What are you talking about, this pseudo-code has a lot more bugs ;)
OK, at least I certainly agree that this approach needs more changes in copy_process().
> > This also makes another difference in multi-threaded case, a signal with a handler > > sent to a forking process will be re-targeted to another thread which can handle it; > > with your patch this signal will be "blocked" until fork() finishes or until another > > thread gets TIF_SIGPENDING. Not that I think this is that important, > > but still. > > I would not object to wants_signal deciding that a task in the middle of > copy_process does not want signals.
This is not enough, we need to signal all in-fork threads...
Oleg.
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