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From: Tom Gundersen <teg@jklm.no>
Date: Fri, 28 Oct 2016 15:18:59 +0200
Message-ID: <CAG-2HqVw64ewD3Tj68g+2M-+SZbRdO_GfkVKHEadutKyerv2vA@mail.gmail.com>
Subject: Re: [RFC v1 08/14] bus1: implement peer management context
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@amacapital.net>, Jiri Kosina <jikos@kernel.org>,
        Greg KH <greg@kroah.com>, Hannes Reinecke <hare@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>, Arnd Bergmann <arnd@arndb.de>,
        Josh Triplett <josh@joshtriplett.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
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On Fri, Oct 28, 2016 at 2:06 PM, Richard Weinberger
<richard.weinberger@gmail.com> wrote:
> David, Tom,
>
> On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> +struct bus1_peer *bus1_peer_new(void)
>> +{
>> +       static atomic64_t peer_ids = ATOMIC64_INIT(0);
>> +       const struct cred *cred = current_cred();
>> +       struct bus1_peer *peer;
>> +       struct bus1_user *user;
>> +
>> +       user = bus1_user_ref_by_uid(cred->uid);
>> +       if (IS_ERR(user))
>> +               return ERR_CAST(user);
>> +
>> +       peer = kmalloc(sizeof(*peer), GFP_KERNEL);
>> +       if (!peer) {
>> +               bus1_user_unref(user);
>> +               return ERR_PTR(-ENOMEM);
>> +       }
>> +
>> +       /* initialize constant fields */
>> +       peer->id = atomic64_inc_return(&peer_ids);
>
> What is the purpose of this id? Do other components depend on it
> and are they aware of possible overflows?

The id is used purely to give a name to the peer in debugfs.

> Since it is an 64bit integer overflowing it is hard but not impossible.

Hm, what scenario do you have in mind? I cannot see how this could
happen (short of creating peers in a loop for hundreds of years).

Cheers,

Tom