Date: Wed, 16 Nov 2016 11:18:37 +0100
From: Greg KH <gregkh@linuxfoundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>, Will Deacon <will.deacon@arm.com>,
        "Reshetova, Elena" <elena.reshetova@intel.com>,
        Arnd Bergmann <arnd@arndb.de>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        David Windsor <dave@progbits.org>, LKML <linux-kernel@vger.kernel.org>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [RFC][PATCH 2/7] kref: Add kref_read()
Message-ID: <20161116101837.GA23902@kroah.com>
References: <20161114173946.501528675@infradead.org>
 <20161114174446.486581399@infradead.org>
 <20161115073322.GC28248@kroah.com>
 <20161115080314.GD3142@twins.programming.kicks-ass.net>
 <CAGXu5jLNduviFkM1A4ozub_n2uB2nAHrhE41BsPFJZq+uhn4Mg@mail.gmail.com>
 <20161116082151.GA24017@kroah.com>
 <20161116101042.GN3142@twins.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20161116101042.GN3142@twins.programming.kicks-ass.net>
User-Agent: Mutt/1.7.1 (2016-10-04)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 814
Lines: 23

On Wed, Nov 16, 2016 at 11:10:42AM +0100, Peter Zijlstra wrote:
> On Wed, Nov 16, 2016 at 09:21:51AM +0100, Greg KH wrote:
> > > What should we do about things like this (bpf_prog_put() and callbacks
> > > from kernel/bpf/syscall.c):
> > > 
> > > 
> > > static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
> > > {
> > >         struct user_struct *user = prog->aux->user;
> > > 
> > >         atomic_long_sub(prog->pages, &user->locked_vm);
> > 
> > Oh that's scary.  Let's just make one reference count rely on another
> > one and not check things...
> 
> Its not a reference count, its a resource limit thingy. Also, isn't
> stacking, or in general building an object graph, the entire point of
> reference counts?

Ah, that wasn't obvious, but yes, you are correct here, sorry for the
noise.

greg k-h