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

[Sergey Dyasly <dserrg@gmail.com>]

Hi, Oleg

Adding thread_head into task_struct->signal would be the best solution imho.
This way list will be properly protected by rcu_read_lock(). But you called it
"really painful". I guess that's because all users of while_each_thread(g, t)
must be modified with 'g' pointing to the new thread_head. And I've counted
50 usages of while_each_thread() across the kernel.

Is this really that bad?

Regards.


On Thu, 2 May 2013 19:20:22 +0200
Oleg Nesterov <oleg@redhat.com> wrote:

> Just to let you know that this time I didn't forget about this problem ;)
> 
> On 04/25, Oleg Nesterov wrote:
> >
> > On 04/25, Sergey Dyasly wrote:
> > >
> > > But in general case there is still a race,
> >
> > Yes. Every while_each_thread() in oom-kill is wrong, and I am still not
> > sure what should/can we do. Will try to think more.
> 
> And I still can't find a simple/clean solution.
> 
> OK. I am starting to think we should probably switch to Plan B. We can add
> thread_head into task_struct->signal and convert while_each_thread() into
> list_for_each_rcu(). This should work, but this is really painful and I was
> going to avoid this as much as possible...
> 
> I'll try to do something once I return from vacation (May 9). Heh, See also
> http://marc.info/?l=linux-kernel&m=127688978121665 and the whole thread.
> 
> Oleg.
> 


-- 
Sergey Dyasly <dserrg@gmail.com>

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