From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3A26C49ED9 for ; Thu, 12 Sep 2019 10:25:14 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B31AE20692 for ; Thu, 12 Sep 2019 10:25:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B31AE20692 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1i8MHc-00049V-8x; Thu, 12 Sep 2019 10:25:00 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1i8MHb-00049F-8f for xen-devel@lists.xenproject.org; Thu, 12 Sep 2019 10:24:59 +0000 X-Inumbo-ID: 91bb2cce-d547-11e9-83e6-12813bfff9fa Received: from mx1.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 91bb2cce-d547-11e9-83e6-12813bfff9fa; Thu, 12 Sep 2019 10:24:58 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 34BD6AF47; Thu, 12 Sep 2019 10:24:57 +0000 (UTC) Message-ID: <08af44affecf2f635afc0ff1e1f377651866d78b.camel@suse.com> From: Dario Faggioli To: Juergen Gross , xen-devel@lists.xenproject.org Date: Thu, 12 Sep 2019 12:24:51 +0200 In-Reply-To: <20190809145833.1020-31-jgross@suse.com> References: <20190809145833.1020-1-jgross@suse.com> <20190809145833.1020-31-jgross@suse.com> Organization: SUSE User-Agent: Evolution 3.32.4 MIME-Version: 1.0 Subject: Re: [Xen-devel] [PATCH v2 30/48] xen/sched: introduce unit_runnable_state() X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Robert VanVossen , Tim Deegan , Julien Grall , Josh Whitehead , Meng Xu , Jan Beulich Content-Type: multipart/mixed; boundary="===============4414281846376508431==" Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" --===============4414281846376508431== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-vbQxU2DbMKz2WftpD2J0" --=-vbQxU2DbMKz2WftpD2J0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2019-08-09 at 16:58 +0200, Juergen Gross wrote: > Today the vcpu runstate of a new scheduled vcpu is always set to > "running" even if at that time vcpu_runnable() is already returning > false due to a race (e.g. with pausing the vcpu). >=20 > With core scheduling this can no longer work as not all vcpus of a > schedule unit have to be "running" when being scheduled. So the > vcpu's > new runstate has to be selected at the same time as the runnability > of > the related schedule unit is probed. >=20 So, you're saying that this patch is meant at fixing a race. A race that, if I understood correctly, it's not there/it's not problematic right now, but will be when we have more than 1 vcpu in a unit and we enable core scheduling. Is this the case? If yes: - this very patch, at this point in the series, is basically introducing no functional (or at least behavioral) change, is this right too? - can you provide some more detail about the race. When/how it occurs and how the changes done in credit and rt fix it? Thanks and Regards --=20 Dario Faggioli, Ph.D http://about.me/dario.faggioli Virtualization Software Engineer SUSE Labs, SUSE https://www.suse.com/ ------------------------------------------------------------------- <> (Raistlin Majere) --=-vbQxU2DbMKz2WftpD2J0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEES5ssOj3Vhr0WPnOLFkJ4iaW4c+4FAl16HPQACgkQFkJ4iaW4 c+5laxAA3DErsducXHK1nL4QHFH1bNP3EI3bSH5cXkv8zIJ6DpkDNi4mj0CyBUcB /1/aGUrJjParXscK9Km3e7hnk7BIjQcdmqVGFYW/RoHbKUWtr5ZsTslsesZh+wpV 9T2Q9l+/a/G/A+hTBDXA3w2j4MEzi+aPdDO6DfJRK5UP7PR6RJXVXlIguKsuqKF2 3h/V71tr2YC/Q9rYCB8v87ry/9ZklO5hd0nxoV8gD8bANR7DBtYgFNX9Q6bLSE3o ZBaVX5KvQd580yERxrzjqB3vp8A+zGdhMEAGMkyS41tcPKyJqyba3U0DldsUjJIN VKqu7mlHn8zFpf08ddtVNM+gi/cMJtBGAxoB0xpDsJNUv1Xm/kNGUvWfebYw+7X5 70HHj8Vap4QaD6S1MVeYc4q5ZWHzW5VbmK7LHd4/VKiadLqs5gbbCSUydAIr4dBC /O83gkHeDhbeOE41y26DYjT0TkJMaNjyF7wqKBkeOXovK+PbsCaQCsazP7RgkYLp OdHs3aewfAGZK32mBAj5zOohOfRkQJ7Yv0vZKPAAw86gjMoAUeGZo3x8Fr28fTTY eoz+9KbxhvdXBW91591nsaHvSu/UYh68KMiQd9dtWuRf2s93rKjnuoQ6b/vXfoCn COLF/SHQmCe68O/i2bx+BejhbeX27NE8Hq9gBi3myW2RmFNHsVc= =TTxb -----END PGP SIGNATURE----- --=-vbQxU2DbMKz2WftpD2J0-- --===============4414281846376508431== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9saXN0 cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== --===============4414281846376508431==--