From patchwork Thu Oct 10 01:13:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Yang X-Patchwork-Id: 1174219 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.intel.com 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 ozlabs.org (Postfix) with ESMTPS id 46pY6x3mpwz9sDQ for ; Thu, 10 Oct 2019 12:15:37 +1100 (AEDT) Received: from localhost ([::1]:33112 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIN3G-00088x-QI for incoming@patchwork.ozlabs.org; Wed, 09 Oct 2019 21:15:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49157) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIN2a-000868-K2 for qemu-devel@nongnu.org; Wed, 09 Oct 2019 21:14:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iIN2Z-00066Y-Gc for qemu-devel@nongnu.org; Wed, 09 Oct 2019 21:14:52 -0400 Received: from mga03.intel.com ([134.134.136.65]:16855) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iIN2Z-0005aN-8P for qemu-devel@nongnu.org; Wed, 09 Oct 2019 21:14:51 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Oct 2019 18:13:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,278,1566889200"; d="scan'208";a="197087540" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga003.jf.intel.com with ESMTP; 09 Oct 2019 18:13:45 -0700 From: Wei Yang To: quintela@redhat.com, dgilbert@redhat.com, peterx@redhat.com Subject: [PATCH v2 2/2] migration/postcopy: check PostcopyState before setting to POSTCOPY_INCOMING_RUNNING Date: Thu, 10 Oct 2019 09:13:16 +0800 Message-Id: <20191010011316.31363-3-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191010011316.31363-1-richardw.yang@linux.intel.com> References: <20191010011316.31363-1-richardw.yang@linux.intel.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.65 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, Wei Yang Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Currently, we set PostcopyState blindly to RUNNING, even we found the previous state is not LISTENING. This will lead to a corner case. First let's look at the code flow: qemu_loadvm_state_main() ret = loadvm_process_command() loadvm_postcopy_handle_run() return -1; if (ret < 0) { if (postcopy_state_get() == POSTCOPY_INCOMING_RUNNING) ... } >From above snippet, the corner case is loadvm_postcopy_handle_run() always sets state to RUNNING. And then it checks the previous state. If the previous state is not LISTENING, it will return -1. But at this moment, PostcopyState is already been set to RUNNING. Then ret is checked in qemu_loadvm_state_main(), when it is -1 PostcopyState is checked. Current logic would pause postcopy and retry if PostcopyState is RUNNING. This is not what we expect, because postcopy is not active yet. This patch makes sure state is set to RUNNING only previous state is LISTENING by checking the state first. Signed-off-by: Wei Yang Suggested by: Peter Xu Reviewed-by: Dr. David Alan Gilbert --- migration/savevm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/migration/savevm.c b/migration/savevm.c index 78c2965ca4..b9f30a7090 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1934,7 +1934,7 @@ static void loadvm_postcopy_handle_run_bh(void *opaque) /* After all discards we can start running and asking for pages */ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis) { - PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_RUNNING); + PostcopyState ps = postcopy_state_get(); trace_loadvm_postcopy_handle_run(); if (ps != POSTCOPY_INCOMING_LISTENING) { @@ -1942,6 +1942,7 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis) return -1; } + postcopy_state_set(POSTCOPY_INCOMING_RUNNING); mis->bh = qemu_bh_new(loadvm_postcopy_handle_run_bh, mis); qemu_bh_schedule(mis->bh);