From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: I/O operations priority in RTOS Date: Sun, 05 Jun 2011 11:25:43 +0200 Message-ID: <4DEB4B97.9030005@web.de> References: <4DEA1BA9.7020303@unican.es> <4DEA1F22.6000603@unican.es> <20110604234214.GA30640@opentech.at> <4DEB427F.9020104@steinhoff.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig3C7E8DAA52B1364594CCC058" Cc: Nicholas Mc Guire , Monica Puig-Pey , linux-rt-users@vger.kernel.org To: Armin Steinhoff Return-path: Received: from fmmailgate02.web.de ([217.72.192.227]:60622 "EHLO fmmailgate02.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755596Ab1FEJZp (ORCPT ); Sun, 5 Jun 2011 05:25:45 -0400 In-Reply-To: <4DEB427F.9020104@steinhoff.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3C7E8DAA52B1364594CCC058 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2011-06-05 10:46, Armin Steinhoff wrote: > Nicholas Mc Guire wrote: >> On Sat, 04 Jun 2011, Monica Puig-Pey wrote: >> >>> Hello, >>> I'm studying how to develop drivers in a real time OS and how do they= >>> work. I'm using Ubuntu 10.04 with the 2.6.31-11-rt patch installed. >>> I would like to know the priority when executing open(), read(), writ= e() >>> and close() operations. >>> In my example the thread which is using the driver runs with 10 RTPRI= O, >>> but I don't know what happens in kernel context with the priority whe= n >>> running the I/O operations. >>> Thank you for your help, I don't know where to learn about this. >>> >> [] >> Also when using bottom half mechanisms you need to take into account t= he >> priority of the kernel thread that manages the defered work items, so >> rt-drivers may have a different structure than normal drivers. >=20 > That's the reason why I prefer UIO based user space drivers ! =2E..which are forced to use threaded IRQs over -rt as well. Taking threaded IRQs out of the picture, bottom-half mechanisms usually come into play when dispatch workload that cannot be assigned to a specific user context is significant. But then UIO is the wrong approach anyway as it doesn't match well the requirements of multi-user device interfaces. Jan --------------enig3C7E8DAA52B1364594CCC058 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAk3rS5cACgkQitSsb3rl5xQWPACfcLmPIOQ8nTZHiLFQPdqY/AV+ dd4An3jDjCmztKX8JEIaVVKzq6F/TPs1 =x4nq -----END PGP SIGNATURE----- --------------enig3C7E8DAA52B1364594CCC058--