Re: [PATCH] oom: add pending SIGKILL check for chosen victim

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 24 Apr 2013 17:42:16 +0200 Oleg Nesterov <oleg@redhat.com> wrote:

> On 04/24, Michal Hocko wrote:
> >
> > On Wed 24-04-13 16:55:14, Oleg Nesterov wrote:
> > >
> > > But I can't understand how this patch can fix the problem, I think it
> > > can't.
> > >
> > > From the changelog:
> > >
> > > 	When SIGKILL is sent to a task, it's also sent to all tasks in the same
> > > 	threadgroup. This information can be used to prevent triggering further
> > > 	oom killers for this threadgroup and avoid the infinite loop.
> > >                                              ^^^^^^^^^^^^^^^^^^^^^^^
> > >
> > > How??
> >
> > I guess it assumes that fatal_signal_pending() is still true even when
> > the process is unhashed already.
> 
> No, it is not (in general). The task can dequeue this SIGKIL and then
> exit. But this doesn't matter.
> 
> > Which sounds like a workaround to me.
> 
> The task can do everything after we check PF_EXITING or whatever else.
> Just suppose it is alive and running, but before we take tasklist_lock
> it exits and removes itself from list.
> 
> But wait, I forgot that "p" is not necessarily the main thread, so
> the patch I sent is not enough...
> 
> Oh, and this reminds me again but we can race with exec... but this
> is mostly theoretical. should be fixed anyway.
> 
> I'll try to think more tomorrow. I need to recall the previous discussion
> at least.

Where does this leave us with Sergey's patch?  "Still good, but
requires new changelog"?

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