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Date:   Wed, 2 Mar 2022 13:52:01 -0800
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Shakeel Butt <shakeelb@google.com>,
        Colin Ian King <colin.king@canonical.com>,
        NeilBrown <neilb@suse.de>, Vasily Averin <vvs@virtuozzo.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Linux MM <linux-mm@kvack.org>, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, Tejun Heo <tj@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Eric Dumazet <edumazet@google.com>,
        Kees Cook <keescook@chromium.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>, linux-kernel@vger.kernel.org,
        kernel@openvz.org
Subject: Re: [PATCH RFC] net: memcg accounting for veth devices
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On Wed, Mar 02, 2022 at 08:43:54AM -0600, Eric W. Biederman wrote:
> Luis Chamberlain <mcgrof@kernel.org> writes:
> 
> > On Tue, Mar 01, 2022 at 02:50:06PM -0600, Eric W. Biederman wrote:
> >> I really have not looked at this pids controller.
> >> 
> >> So I am not certain I understand your example here but I hope I have
> >> answered your question.
> >
> > During experimentation with the above stress-ng test case, I saw tons
> > of thread just waiting to do exit:
> 
> You increment the count of concurrent threads after a no return function
> in do_exit.  Since the increment is never reached the count always goes
> down and eventually the warning prints.
> 
> > diff --git a/kernel/exit.c b/kernel/exit.c
> > index 80c4a67d2770..653ca7ebfb58 100644
> > --- a/kernel/exit.c
> > +++ b/kernel/exit.c
> > @@ -881,6 +894,9 @@ void __noreturn do_exit(long code)
> >  
> >  	lockdep_free_task(tsk);
> >  	do_task_dead();
> 
> The function do_task_dead never returns.
> 
> > +
> > +	atomic_inc(&exit_concurrent_max);
> > +	wake_up(&exit_wq);
> >  }
> >  EXPORT_SYMBOL_GPL(do_exit);

Doh thanks!

  Luis