Re: [RFC 14/18] limits: track RLIMIT_SIGPENDING actual max

From: Oleg Nesterov <oleg@redhat.com>
To: Topi Miettinen <toiwoton@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Amanieu d'Antras" <amanieu@gmail.com>,
	Stas Sergeev <stsp@list.ru>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Wang Xiaoqiang <wangxq10@lzu.edu.cn>,
	Helge Deller <deller@gmx.de>,
	Sasha Levin <sasha.levin@oracle.com>
Subject: Re: [RFC 14/18] limits: track RLIMIT_SIGPENDING actual max
Date: Tue, 14 Jun 2016 16:50:20 +0200	[thread overview]
Message-ID: <20160614145019.GA32429@redhat.com> (raw)
In-Reply-To: <1465847065-3577-15-git-send-email-toiwoton@gmail.com>

On 06/13, Topi Miettinen wrote:
>
> Track maximum number of pending signals, presented in /proc/self/limits.
>
> Signed-off-by: Topi Miettinen <toiwoton@gmail.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.