From patchwork Wed Mar 3 17:05:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12113923 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 D6323C433DB for ; Wed, 3 Mar 2021 17:06:19 +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 3038C64E25 for ; Wed, 3 Mar 2021 17:06:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3038C64E25 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.92922.175248 (Exim 4.92) (envelope-from ) id 1lHUwI-00054s-5P; Wed, 03 Mar 2021 17:05:34 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 92922.175248; Wed, 03 Mar 2021 17:05:34 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHUwI-00054l-1P; Wed, 03 Mar 2021 17:05:34 +0000 Received: by outflank-mailman (input) for mailman id 92922; Wed, 03 Mar 2021 17:05:32 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHUwG-00054f-M4 for xen-devel@lists.xenproject.org; Wed, 03 Mar 2021 17:05:32 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lHUwF-0004yA-4M; Wed, 03 Mar 2021 17:05:31 +0000 Received: from 54-240-197-235.amazon.com ([54.240.197.235] helo=ufe34d9ed68d054.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lHUwE-0005q4-Ip; Wed, 03 Mar 2021 17:05:30 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Message-Id:Date:Subject:Cc:To:From; bh=9yPzP18IxQGu4Rh4EpOr1irO50bzzkHI1YvhVzGWuy8=; b=TmaV2u0t8q9F/Mbs3Bj88nGH4o Z1RRUcYfDXy1PM2L4g096zfl4uEjtehqGrl/Yd279G+iwYw4IEkUiTx+Di/xiq09v0c8Cil4LsoPJ mmTZL/S/TVKUxB9E2kflpg2mJm8uc712hhgrDjN5bd8+7QRLKqxi0OnvuppxEHz1N0EQ=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: raphning@amazon.co.uk, iwj@xenproject.org, Julien Grall , Wei Liu , Juergen Gross , Bjoern Doebel Subject: [PATCH for-4.15] tools/xenstored: liveupdate: Properly check long transaction Date: Wed, 3 Mar 2021 17:05:26 +0000 Message-Id: <20210303170526.15903-1-julien@xen.org> X-Mailer: git-send-email 2.17.1 From: Julien Grall As XenStored is single-threaded, conn->ta_start_time will always be smaller than now. As we substract the latter from the former, it means a transaction will never be considered long running. Invert the two operands of the substraction in both lu_reject_reason() and lu_check_allowed(). In addition to that, the former also needs to check that conn->ta_start_time is not 0 (i.e the transaction is not active). Take the opportunity to document the return condition of lu_check_allowed(). Fixes: e04e53a5be20 ("tools/xenstore: allow live update only with no transaction active") Reported-by: Bjoern Doebel Signed-off-by: Julien Grall Reviewed-by: Juergen Gross --- I am a bit puzzled on how -F is implemented. From my understanding we will force LiveUpdate when one of the following conditions is met: 1) All the active transactions are long running 2) If we didn't manage to LiveUpdate after N sec It is not quite clear why we need the both as 2) would indirectly cover 1). However 2) is probably unsafe as we may reset transactions for "well-behaving" guest. So I am thinking to send a patch to drop 2). Any opinions? This patch is candidate for 4.15. Without it, the long-running transactions are not properly accounted. --- tools/xenstore/xenstored_control.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/tools/xenstore/xenstored_control.c b/tools/xenstore/xenstored_control.c index d7ad112138b2..8e470f2b2056 100644 --- a/tools/xenstore/xenstored_control.c +++ b/tools/xenstore/xenstored_control.c @@ -459,11 +459,18 @@ static bool lu_check_lu_allowed(void) list_for_each_entry(conn, &connections, list) { if (conn->ta_start_time) { ta_total++; - if (conn->ta_start_time - now >= lu_status->timeout) + if (now - conn->ta_start_time >= lu_status->timeout) ta_long++; } } + /* + * Allow LiveUpdate if one of the following conditions is met: + * - There is no active transactions + * - All transactions are long running (e.g. they have been + * active for more than lu_status->timeout sec) and the admin as + * requested to force the operation. + */ return ta_total ? (lu_status->force && ta_long == ta_total) : true; } @@ -474,11 +481,12 @@ static const char *lu_reject_reason(const void *ctx) time_t now = time(NULL); list_for_each_entry(conn, &connections, list) { - if (conn->ta_start_time - now >= lu_status->timeout) { + if (conn->ta_start_time && + (now - conn->ta_start_time >= lu_status->timeout)) { ret = talloc_asprintf(ctx, "%s\nDomain %u: %ld s", ret ? : "Domains with long running transactions:", conn->id, - conn->ta_start_time - now); + now - conn->ta_start_time); } }