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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BA58CEE020F for ; Wed, 13 Sep 2023 21:54:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qgXnc-0004cd-DY; Wed, 13 Sep 2023 17:53:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qgXnb-0004cR-6l for qemu-devel@nongnu.org; Wed, 13 Sep 2023 17:53:27 -0400 Received: from smtp-out1.suse.de ([2001:67c:2178:6::1c]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qgXnZ-0001Tc-G0 for qemu-devel@nongnu.org; Wed, 13 Sep 2023 17:53:26 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 15E54215E6; Wed, 13 Sep 2023 21:53:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1694642004; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O2WOgp3IZfd/6UhwnsAkaKgM2lYZ4ASBTBX+ueRMarw=; b=B9tcg1jdaDbOZ0woCU4m+cPHti9gijmZhlS8oIHeKfSLtIqFkiXISsXH2ljx09aMqwt0Bh dvi1a4JEWNVnJDVVdW/a3yJEj9uLcv9bdiVmPG8/Vf94je82QbmPn938pDd3VJLdwl3ILi iREcKMuSE1PqB/uocqcso9uwkBiWB+Q= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1694642004; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O2WOgp3IZfd/6UhwnsAkaKgM2lYZ4ASBTBX+ueRMarw=; b=0J/+zDkSsbwQB8Ox08V/967mguBf2beXGxUm98tXr31ti/tdkIFQgMnz8Um/F4YnlUqNVT 4OTjn7CiSZmgHPDA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 7F02213440; Wed, 13 Sep 2023 21:53:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id lsWgD1MvAmXIJgAAMHmgww (envelope-from ); Wed, 13 Sep 2023 21:53:23 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, Juan Quintela , Lukas Straub , Leonardo Bras Subject: Re: [PATCH v6 09/10] migration/yank: Keep track of registered yank instances In-Reply-To: References: <20230911171320.24372-1-farosas@suse.de> <20230911171320.24372-10-farosas@suse.de> Date: Wed, 13 Sep 2023 18:53:20 -0300 Message-ID: <87jzstkaen.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=2001:67c:2178:6::1c; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > On Mon, Sep 11, 2023 at 02:13:19PM -0300, Fabiano Rosas wrote: >> The core yank code is strict about balanced registering and >> unregistering of yank functions. >> >> This creates a difficulty because the migration code registers one >> yank function per QIOChannel, but each QIOChannel can be referenced by >> more than one QEMUFile. The yank function should not be removed until >> all QEMUFiles have been closed. >> >> Keep a reference count of how many QEMUFiles are using a QIOChannel >> that has a yank function. Only unregister the yank function when all >> QEMUFiles have been closed. >> >> This improves the current code by removing the need for the programmer >> to know which QEMUFile is the last one to be cleaned up and fixes the >> theoretical issue of removing the yank function while another QEMUFile >> could still be using the ioc and require a yank. >> >> Signed-off-by: Fabiano Rosas >> --- >> migration/yank_functions.c | 81 ++++++++++++++++++++++++++++++++++---- >> migration/yank_functions.h | 8 ++++ >> 2 files changed, 81 insertions(+), 8 deletions(-) > > I worry this over-complicate things. It does. We ran out of simple options. > If you prefer the cleaness that we operate always on qemufile level, can we > just register each yank function per-qemufile? "just" hehe we could, but: i) the yank is a per-channel operation, so this is even more unintuitive; ii) multifd doesn't have a QEMUFile, so it will have to continue using the ioc; iii) we'll have to add a yank to every new QEMUFile created during the incoming migration (colo, rdma, etc), otherwise the incoming side will be left using iocs while the src uses the QEMUFile; iv) this is a functional change of the yank feature for which we have no tests. If that's all ok to you I'll go ahead and git it a try. > I think qmp yank will simply fail the 2nd call on the qemufile if the > iochannel is shared with the other one, but that's totally fine, IMHO. > > What do you think? > > In all cases, we should probably at least merge patch 1-8 if that can > resolve the CI issue. I think all of them are properly reviewed. I agree. Someone needs to queue this though since Juan has been busy.