From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Kleine-Budde Subject: Re: What are you doing if the TX buffer overflows? Date: Wed, 19 Sep 2012 09:31:13 +0200 Message-ID: <505974C1.8080907@pengutronix.de> References: <505777BC.3000705@hartkopp.net> <5058659E.2010804@grandegger.com> <50586A50.5060300@pengutronix.de> <50586DE4.9020707@grandegger.com> <50587058.7090703@pengutronix.de> <50587987.3070308@grandegger.com> <50587A4F.5060105@pengutronix.de> <5058C28A.5030300@grandegger.com> <5058C505.6020605@pengutronix.de> <5058C7EC.1080206@grandegger.com> <20120918202018.GA78585@macbook.local> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigB7B1AC4ABC0E5158BA10EEC6" Return-path: Received: from metis.ext.pengutronix.de ([92.198.50.35]:41569 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754169Ab2ISHbR (ORCPT ); Wed, 19 Sep 2012 03:31:17 -0400 In-Reply-To: <20120918202018.GA78585@macbook.local> Sender: linux-can-owner@vger.kernel.org List-ID: To: Wolfgang Grandegger , Oliver Hartkopp , =?UTF-8?B?SGVpbnotSsO8cmdlbiBPZXJ0ZWw=?= , "linux-can@vger.kernel.org" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigB7B1AC4ABC0E5158BA10EEC6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 09/18/2012 10:20 PM, Kurt Van Dijck wrote: > On Tue, Sep 18, 2012 at 09:13:48PM +0200, Wolfgang Grandegger wrote: >> On 09/18/2012 09:01 PM, Marc Kleine-Budde wrote: >>> On 09/18/2012 08:50 PM, Wolfgang Grandegger wrote: >>>> On 09/18/2012 03:42 PM, Marc Kleine-Budde wrote: >>>>> On 09/18/2012 03:39 PM, Wolfgang Grandegger wrote: >>>>>> On 09/18/2012 03:00 PM, Marc Kleine-Budde wrote: >>>>>>> On 09/18/2012 02:49 PM, Wolfgang Grandegger wrote: >>>>>>> [...] >>>>>>> >>>>>>>>> We have several customers who asked how to abort pending TX mes= sages, >>>>>>>>> too. Which involves: >>>>>>>>> a) clear the TX-queue in Linux >>>>>>>>> b) clear queue in hardware >>>>>>>>> c) abort currently transmitting CAN frame >>>>>>>>> >>>>>>>>> I think c) would be a usecase of its own, too. >>>>>>>> >>>>>>>> I think you need c) for b), at least for some controllers. These= >>>>>>> >>>>>>> Yes, if it's a hardware limitation so be it. But if we design an >>>>>>> interface it should support "clear everything" (a+b+c), but also = just >>>>>>> only c. >>>>>> >>>>>> Yes, that you be nice. The only portable "clear everything" (a+b+c= ) I >>>>>> see is "ifconfig down -> up". This also answers you other related = mail. >>>>>> >>>>>> What do people really want/need and why? This is still not clear t= o me. >>>>>> More input would be nice. >>>>> >>>>> Heinz-J=C3=BCrgen uses abort current TX Message on SJA1000, can you= give us >>>>> more insight? I've talked to customers, e.g. they want to abort the= >>>>> current frame if it takes "too long" to send it, because the frames= CAN >>>>> id priority is too low. >=20 > If "too long" is defined as a period of time where it makes sense to > take such actions in software (like > 10msec), and your message still > did not get out, but you wanted it to be, > then IMO the bus load is too high with regard to the expected time rest= rictions. >=20 > Or am I missing something? >=20 >>>> >>>> What we could implement rather easily is a "tx-abort-last" or >>>> "tx-abort-all" netlink command. As this command does not make sense = when >>>> more than one message is pending I'm in favor of "tx-abort-last". >>> >>> I like to have both commands. >> >> But then "tx-abort-all" should also clear the tx socket queue. Also be= >> aware that more than one socket may send messages. Let's wait for more= >> use-cases. >=20 > I'm afraid tx-abort-all & tx-abort-last cause more damage than good, > especially, but not only, in multi-user environments. Yes, sure, they might, but so a "ifconfig down; ifconfig up" does. But "tx-abort-last" is a valid use case. IIRC even the FPGA CAN controller I've seen on the CIA meeting implemented something like this. Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | --------------enigB7B1AC4ABC0E5158BA10EEC6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iEYEARECAAYFAlBZdMEACgkQjTAFq1RaXHM9MwCgjZdlvYofE6g0Vy0H98BQp6Qu Pd4An3Z00+o7HsHsDn/acHS8KtS+2+u7 =epcV -----END PGP SIGNATURE----- --------------enigB7B1AC4ABC0E5158BA10EEC6--