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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 D113FC433E0 for ; Thu, 9 Jul 2020 11:57:41 +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 944122076A for ; Thu, 9 Jul 2020 11:57:41 +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="SS+JNGW3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 944122076A 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]:60040 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jtVBM-0006BG-To for qemu-devel@archiver.kernel.org; Thu, 09 Jul 2020 07:57:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35782) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jtVAe-0005gU-QD for qemu-devel@nongnu.org; Thu, 09 Jul 2020 07:56:56 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:29057 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jtVAd-0006hW-62 for qemu-devel@nongnu.org; Thu, 09 Jul 2020 07:56:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594295814; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g1ZBGT1zDNLnw/CyFE8o89qKfyZxC5F+6z3b9aNvwcw=; b=SS+JNGW30i2aWADRemA1yxIS3J16KGfoI1pMq/eoB9CoC2JgnqEJVhteSmhzX2j01JqMTH UZVV7TYg8BYj/Tiduh45zg3nDzA3qrCLqDLMrLVN589mMOVX9YpKtiigTUc+kF6rczTu0u EIsVkn+CSp7ZiTqGsdX0UJlqdOQRyYg= 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-326-bU_A6TAnOUiG9Xp3nL5mAQ-1; Thu, 09 Jul 2020 07:56:50 -0400 X-MC-Unique: bU_A6TAnOUiG9Xp3nL5mAQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BE94E88C797; Thu, 9 Jul 2020 11:56:49 +0000 (UTC) Received: from starship (unknown [10.35.206.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 520106FEC2; Thu, 9 Jul 2020 11:56:42 +0000 (UTC) Message-ID: <36fae287a2b5e06c35facf22e5d9c16fbbf9908e.camel@redhat.com> Subject: Re: [PATCH v2 2/7] Implement drain_call_rcu and use it in hmp_device_del From: Maxim Levitsky To: Markus Armbruster Date: Thu, 09 Jul 2020 14:56:41 +0300 In-Reply-To: <87wo3csyn4.fsf@dusky.pond.sub.org> References: <20200511160951.8733-1-mlevitsk@redhat.com> <20200511160951.8733-3-mlevitsk@redhat.com> <87wo3csyn4.fsf@dusky.pond.sub.org> User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlevitsk@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=mlevitsk@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/09 01:47:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H2=-1, 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: Fam Zheng , Daniel =?ISO-8859-1?Q?P=2EBerrang=E9?= , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 2020-07-09 at 13:42 +0200, Markus Armbruster wrote: > Maxim Levitsky writes: > > > This allows to preserve the semantics of hmp_device_del, > > that the device is deleted immediatly which was changed by previos > > patch that delayed this to RCU callback > > > > Suggested-by: Stefan Hajnoczi > > Signed-off-by: Maxim Levitsky > > --- > > include/qemu/rcu.h | 1 + > > qdev-monitor.c | 3 +++ > > util/rcu.c | 33 +++++++++++++++++++++++++++++++++ > > 3 files changed, 37 insertions(+) > > > > diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h > > index 570aa603eb..0e375ebe13 100644 > > --- a/include/qemu/rcu.h > > +++ b/include/qemu/rcu.h > > @@ -133,6 +133,7 @@ struct rcu_head { > > }; > > > > extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); > > +extern void drain_call_rcu(void); > > > > /* The operands of the minus operator must have the same type, > > * which must be the one that we specify in the cast. > > diff --git a/qdev-monitor.c b/qdev-monitor.c > > index 56cee1483f..70877840a2 100644 > > --- a/qdev-monitor.c > > +++ b/qdev-monitor.c > > @@ -812,6 +812,8 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) > > return; > > } > > dev = qdev_device_add(opts, &local_err); > > + drain_call_rcu(); > > + > > if (!dev) { > > error_propagate(errp, local_err); > > qemu_opts_del(opts); > > @@ -904,6 +906,7 @@ void qmp_device_del(const char *id, Error **errp) > > } > > > > qdev_unplug(dev, errp); > > + drain_call_rcu(); > > } > > } > > > > Subject claims "in hmp_device_del", code has it in qmp_device_add() and > qmp_device_del(). Please advise. I added it in both, because addition of a device can fail and trigger removal, which can also be now delayed due to RCU. Since both device_add and device_del aren't used often, the overhead won't be a problem IMHO. Best regards, Maxim Levitsky > > [...]