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 DFCB0C04E69 for ; Mon, 31 Jul 2023 21:14:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qQaCp-00073J-Oz; Mon, 31 Jul 2023 17:13:31 -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 1qQaCo-00072v-DD for qemu-devel@nongnu.org; Mon, 31 Jul 2023 17:13:30 -0400 Received: from smtp-out2.suse.de ([2001:67c:2178:6::1d]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qQaCm-0001Aa-NP for qemu-devel@nongnu.org; Mon, 31 Jul 2023 17:13:30 -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-out2.suse.de (Postfix) with ESMTPS id D12BA1F893; Mon, 31 Jul 2023 21:13:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1690838006; 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=r+QtKAmXQFrsiNdVYrScffUlm6PtW/xKtbgjBYWeEnc=; b=O/X8+6Zo97oQdotdwg+1cSU0WRkNOIxis7Q3u4QMkIZtkstWwyMFNGU1ZhMtM+6OKzmMER mcZH+zHESa0wXn5g5vS70gilIYI/fb4BZP0cGXlXwaVrivnrOQ94sxVM15zfqSkLn0IYiX u91mHBoVF0eKNp282cA5wZOJRQZxbeM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1690838006; 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=r+QtKAmXQFrsiNdVYrScffUlm6PtW/xKtbgjBYWeEnc=; b=IFakzJ5nDo1PnE1Qah06GpQTviLKYmZ/sxSr25nZyq8paTZr/3VGmLL/3QXWEfUBwtkrir x5ePXW2MQCovWMBA== 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 62DCC1322C; Mon, 31 Jul 2023 21:13:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id GSmNC/YjyGTVCwAAMHmgww (envelope-from ); Mon, 31 Jul 2023 21:13:26 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, Juan Quintela , Leonardo Bras Subject: Re: [PATCH 1/3] migration: Stop marking RP bad after shutdown In-Reply-To: <87cz07yetb.fsf@suse.de> References: <20230728121516.16258-1-farosas@suse.de> <20230728121516.16258-2-farosas@suse.de> <87cz07yetb.fsf@suse.de> Date: Mon, 31 Jul 2023 18:13:24 -0300 Message-ID: <87a5vbyebv.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=2001:67c:2178:6::1d; envelope-from=farosas@suse.de; helo=smtp-out2.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, T_SCC_BODY_TEXT_LINE=-0.01 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 Fabiano Rosas writes: > Peter Xu writes: > >> On Fri, Jul 28, 2023 at 09:15:14AM -0300, Fabiano Rosas wrote: >>> When waiting for the return path (RP) thread to finish, there is >>> really nothing wrong in the RP if the destination end of the migration >>> stops responding, leaving it stuck. >>> >>> Stop returning an error at that point and leave it to other parts of >>> the code to catch. One such part is the very next routine run by >>> migration_completion() which checks 'to_dst_file' for an error and fails >>> the migration. Another is the RP thread itself when the recvmsg() >>> returns an error. >>> >>> With this we stop marking RP bad from outside of the thread and can >>> reuse await_return_path_close_on_source() in the next patches to wait >>> on the thread during a paused migration. >>> >>> Signed-off-by: Fabiano Rosas >>> --- >>> migration/migration.c | 1 - >>> 1 file changed, 1 deletion(-) >>> >>> diff --git a/migration/migration.c b/migration/migration.c >>> index 91bba630a8..051067f8c5 100644 >>> --- a/migration/migration.c >>> +++ b/migration/migration.c >>> @@ -2049,7 +2049,6 @@ static int await_return_path_close_on_source(MigrationState *ms) >>> * waiting for the destination. >>> */ >>> qemu_file_shutdown(ms->rp_state.from_dst_file); >>> - mark_source_rp_bad(ms); >>> } >>> trace_await_return_path_close_on_source_joining(); >>> qemu_thread_join(&ms->rp_state.rp_thread); >> >> The retval of await_return_path_close_on_source() relies on >> ms->rp_state.error. If mark_source_rp_bad() is dropped, is it possible >> that it'll start to return succeed where it used to return failure? > > Yep, as described in the commit message, I think it's ok to do that. The > critical part is doing the shutdown. Other instances of > mark_source_rp_bad() continue existing and we continue returning > rp_state.error. > >> >> Maybe not a big deal: I see migration_completion() also has another >> qemu_file_get_error() later to catch errors, but I don't know how solid >> that is. > > That is the instance I refer to in the commit message. At > await_return_path_close_on_source() we only call mark_source_rp_bad() if > to_dst_file has an error. That will be caught by this > qemu_file_get_error() anyway. Actually, I can do better, I can merge this shutdown() into migration_completion(). Then this dependency becomes explicit. Since you suggested moving await_return_path_close_on_source() into postcopy_pause(), it doesn't make sense to check to_dst_file anymore, because when pausing we clear that file.