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=-11.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 796BFC388F9 for ; Wed, 21 Oct 2020 19:03:31 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id EA0B22177B for ; Wed, 21 Oct 2020 19:03:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MpJk29rQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA0B22177B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:60390 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kVJOT-00027n-R8 for qemu-devel@archiver.kernel.org; Wed, 21 Oct 2020 15:03:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43426) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kVJHr-0003Dg-IO for qemu-devel@nongnu.org; Wed, 21 Oct 2020 14:56:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46924) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kVJHp-0000Fp-2h for qemu-devel@nongnu.org; Wed, 21 Oct 2020 14:56:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603306595; h=from:from:reply-to:subject:subject: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=R4uvtJuso9ItIBwRyQz/MMjjUFjkmicafahCQi65c1Y=; b=MpJk29rQTweI7YzattavTzY0XEuYwoqHHg5NKJCRaKFsAkn5CjrEOq5kuohp/hrLtgQZmu ofibZDuIlRBwx38sMtW+L43By4291YgLtYWbxEoJqnZrx/U/zL67h4mot0Me3dQ/VBzugf Yc6OalEEMj93GizxgMpbEaoeKH56LHk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-511-5P9HxveFM7ek1Cz6-UH3zg-1; Wed, 21 Oct 2020 14:56:34 -0400 X-MC-Unique: 5P9HxveFM7ek1Cz6-UH3zg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C033E186DD23; Wed, 21 Oct 2020 18:56:32 +0000 (UTC) Received: from work-vm (ovpn-114-232.ams2.redhat.com [10.36.114.232]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 81AC15C1BD; Wed, 21 Oct 2020 18:56:28 +0000 (UTC) Date: Wed, 21 Oct 2020 19:56:25 +0100 From: "Dr. David Alan Gilbert" To: Peter Xu Subject: Re: [PATCH v5 5/6] migration/postcopy: Release fd before going into 'postcopy-pause' Message-ID: <20201021185625.GH3671@work-vm> References: <20201019225720.172743-1-peterx@redhat.com> <20201019225720.172743-6-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201019225720.172743-6-peterx@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/21 02:16:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Thomas Huth , qemu-devel@nongnu.org, Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Xu (peterx@redhat.com) wrote: > Logically below race could trigger with the old code: > > test program migration thread > ------------ ---------------- > wait_until('postcopy-pause') > postcopy_pause() > set_state('postcopy-pause') > do_postcopy_recover() > arm s->to_dst_file with new fd > release s->to_dst_file [1] > > Here [1] could have released the just-installed recoverying channel. Then the > migration could hang without really resuming. > > Instead, it should be very safe to release the fd before setting the state into > 'postcopy-pause', because there's no reason for any other thread to touch it > during 'postcopy-active'. > > Dave reported a very rare postcopy recovery hang that the migration-test > program waited for the migration to complete in migrate_postcopy_complete(). > We do suspect it's the same thing that we're gonna fix here. Hard to tell. > However since we've noticed this, fix this irrelevant of the hang report. > > Cc: Dr. David Alan Gilbert > Cc: Juan Quintela > Signed-off-by: Peter Xu Reviewed-by: Dr. David Alan Gilbert > --- > migration/migration.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 0b4fcff01f..50df6251b7 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -3182,9 +3182,6 @@ static MigThrError postcopy_pause(MigrationState *s) > while (true) { > QEMUFile *file; > > - migrate_set_state(&s->state, s->state, > - MIGRATION_STATUS_POSTCOPY_PAUSED); > - > /* Current channel is possibly broken. Release it. */ > assert(s->to_dst_file); > qemu_mutex_lock(&s->qemu_file_lock); > @@ -3195,6 +3192,9 @@ static MigThrError postcopy_pause(MigrationState *s) > qemu_file_shutdown(file); > qemu_fclose(file); > > + migrate_set_state(&s->state, s->state, > + MIGRATION_STATUS_POSTCOPY_PAUSED); > + > error_report("Detected IO failure for postcopy. " > "Migration paused."); > > -- > 2.26.2 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK