linux-kernel - Re: [RFC 14/18] limits: track RLIMIT

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Message-ID: <20160614145019.GA32429@redhat.com>
Date:	Tue, 14 Jun 2016 16:50:20 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Topi Miettinen <toiwoton@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Amanieu d'Antras" <amanieu@...il.com>,
	Stas Sergeev <stsp@...t.ru>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Wang Xiaoqiang <wangxq10@....edu.cn>,
	Helge Deller <deller@....de>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [RFC 14/18] limits: track RLIMIT_SIGPENDING actual max

On 06/13, Topi Miettinen wrote:
>
> Track maximum number of pending signals, presented in /proc/self/limits.
>
> Signed-off-by: Topi Miettinen <toiwoton@...il.com>
> ---
>  kernel/signal.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 96e9bc4..c8fbccd 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -387,6 +387,8 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
>  		INIT_LIST_HEAD(&q->list);
>  		q->flags = 0;
>  		q->user = user;
> +		/* XXX resource limits apply per task, not per user */
> +		bump_rlimit(RLIMIT_SIGPENDING, atomic_read(&user->sigpending));

Well, I have to admit that I too dislike the very idea of these changes...

But this particular patch looks wrong in any case. I wasn't cc'ed on the
previous patches which add bump_rlimit(), but I have found

	"[RFC 05/18] limits: track and present RLIMIT_NOFILE actual max"
	http://marc.info/?l=linux-fsdevel&m=146584742331072&w=2

and bump_rlimit() changes current->signal->rlim_curmax, while in this case
you need to bump t->signal->rlim_curmax.

Oleg.