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Mon, 26 Oct 2020 10:32:15 -0400 (EDT) Date: Mon, 26 Oct 2020 08:32:13 -0600 From: Tycho Andersen To: "Michael Kerrisk (man-pages)" Cc: Sargun Dhillon , Christian Brauner , Kees Cook , Daniel Borkmann , Giuseppe Scrivano , Song Liu , Robert Sesek , Containers , linux-man , lkml , Aleksa Sarai , Jann Horn , Alexei Starovoitov , Will Drewry , bpf , Andy Lutomirski Subject: Re: For review: seccomp_user_notif(2) manual page [v2] Message-ID: <20201026143213.GO1884107@cisco> References: <63598b4f-6ce3-5a11-4552-cdfe308f68e4@gmail.com> <20201026135418.GN1884107@cisco> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Oct 26, 2020 at 03:30:29PM +0100, Michael Kerrisk (man-pages) wrote: > Hi Tycho, > > Thanks for getting back to me. > > On Mon, 26 Oct 2020 at 14:54, Tycho Andersen wrote: > > > > On Mon, Oct 26, 2020 at 10:55:04AM +0100, Michael Kerrisk (man-pages) wrote: > > > Hi all (and especially Tycho and Sargun), > > > > > > Following review comments on the first draft (thanks to Jann, Kees, > > > Christian and Tycho), I've made a lot of changes to this page. > > > I've also added a few FIXMEs relating to outstanding API issues. > > > I'd like a second pass review of the page before I release it. > > > But also, this mail serves as a way of noting the outstanding API > > > issues. > > > > > > Tycho: I still have an outstanding question for you at [2]. > > > [2] https://lore.kernel.org/linux-man/8f20d586-9609-ef83-c85a-272e37e684d8@gmail.com/ > > > > I don't have that thread in my inbox any more, but I can reply here: > > no, I don't know any users of this info, but I also don't anticipate > > knowing how people will all use this feature :) > > Yes, but my questions were: > > [[ > [1] So, I think maybe I now understand what you intended with setting > POLLOUT: the notification has been received ("read") and now the > FD can be used to NOTIFY_SEND ("write") a response. Right? > > [2] If that's correct, I don't have a problem with it. I just wonder: > is it useful? IOW: are there situations where the process doing the > NOTIFY_SEND might want to test for POLLOUT because the it doesn't > know whether a NOTIFY_RECV has occurred? > ]] > > So, do I understand right in [1]? (The implication from your reply is > yes, but I want to be sure...) Yes. > For [2], my question was not about users, but *use cases*. The > question I asked myself is: why does the feature exist? Hence my > question [2] reworded: "when you designed this, did you have in mind > scenarios here the process doing the NOTIFY_SEND might need to test > for POLLOUT because it doesn't know whether a NOTIFY_RECV has > occurred?" I did not. Tycho