From nobody Mon Feb 9 02:28:28 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1594825604; cv=none; d=zohomail.com; s=zohoarc; b=UFPmtTKD/lmIZZefgNU5BlEERllqeNNZOCNMpC4PnEg0RmKXHJx2GYkU88lGG8IN7Tamtv5R3cGyTDXyi8NndQngus/A7sCK8Yi1ozbkfZr2g8barb9vXNDfYrEQ0GvHcpMTuvC5uE7Tlevbmpr5bwxrsRFlzhNRDQVkKTmrtj0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1594825604; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=cqQo+2OZgxKCQyPaEbj3n8KYCTJOI/nyva2eHyIbwgQ=; b=XrvnlIdJtIq91rCn5H6LgO+Bp15hNDfLyZgC/hyFKC9tEtgY8G4ObtSlSWqVssYQelrxsu0sJODA0dHvZy/LDXb0crX3/BI26fE/K6SEWMCFcbkBv3n+L6pi0c1LaAbQxBBpCfUv0A0q+CbA6KkZk8tF6aN60AVkZanLuifZuk0= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1594825604089384.226793388411; Wed, 15 Jul 2020 08:06:44 -0700 (PDT) Received: from localhost ([::1]:46422 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jviza-0001nM-Oi for importer@patchew.org; Wed, 15 Jul 2020 11:06:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35170) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jvivQ-00052E-QX for qemu-devel@nongnu.org; Wed, 15 Jul 2020 11:02:24 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:24164 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 1jvivN-0004cu-Qi for qemu-devel@nongnu.org; Wed, 15 Jul 2020 11:02:24 -0400 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-288-BaY9oVgxMhS4-GaBXvkPHA-1; Wed, 15 Jul 2020 11:02:15 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 308C3EED22; Wed, 15 Jul 2020 15:02:14 +0000 (UTC) Received: from starship.redhat.com (unknown [10.35.206.178]) by smtp.corp.redhat.com (Postfix) with ESMTP id CC97F6E9F3; Wed, 15 Jul 2020 15:02:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594825340; 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=cqQo+2OZgxKCQyPaEbj3n8KYCTJOI/nyva2eHyIbwgQ=; b=U1DBIj86skd4ICgOLYtnVP1ClukvYxSoIY0QG8k6hcKF2vH3c12xWvlBzJswzNXbKWyDCL ahMF2Ppo/6mqRQIghOKP7VsrbLh6EMUcQlehbqH/QGRWmpQvghARlKFTy3f/OKUek/cFJ6 0MQAI2SlBDoVwnBJoV3pYA4+EkjkvlQ= X-MC-Unique: BaY9oVgxMhS4-GaBXvkPHA-1 From: Maxim Levitsky To: qemu-devel@nongnu.org Subject: [PATCH v3 2/7] Implement drain_call_rcu and use it in hmp_device_del Date: Wed, 15 Jul 2020 18:01:54 +0300 Message-Id: <20200715150159.95050-3-mlevitsk@redhat.com> In-Reply-To: <20200715150159.95050-1-mlevitsk@redhat.com> References: <20200715150159.95050-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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 = 2020/07/15 02:37:05 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 , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Eduardo Habkost , "Michael S. Tsirkin" , Stefan Hajnoczi , Maxim Levitsky , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" 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 Signed-off-by: Maxim Levitsky Suggested-by: Stefan Hajnoczi Reviewed-by: Stefan Hajnoczi --- include/qemu/rcu.h | 1 + qdev-monitor.c | 22 +++++++++++++++++++ util/rcu.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 78 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 { }; =20 extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); +extern void drain_call_rcu(void); =20 /* 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 71ebce19df..a889fbc509 100644 --- a/qdev-monitor.c +++ b/qdev-monitor.c @@ -803,6 +803,18 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, = Error **errp) return; } dev =3D qdev_device_add(opts, errp); + + /* + * Drain all pending RCU callbacks. This is done because + * some bus related operations can delay a device removal + * (in this case this can happen if device is added and then + * removed due to a configuration error) + * to a RCU callback, but user might expect that this interface + * will finish its job completely once qmp command returns result + * to the user + */ + drain_call_rcu(); + if (!dev) { qemu_opts_del(opts); return; @@ -894,6 +906,16 @@ void qmp_device_del(const char *id, Error **errp) } =20 qdev_unplug(dev, errp); + + /* + * Drain all pending RCU callbacks. This is done because + * some bus related operations can delay a device removal + * to a RCU callback, but user might expect that this interface + * will finish its job completely once qmp command returns result + * to the user + */ + + drain_call_rcu(); } } =20 diff --git a/util/rcu.c b/util/rcu.c index 60a37f72c3..c4fefa9333 100644 --- a/util/rcu.c +++ b/util/rcu.c @@ -293,6 +293,61 @@ void call_rcu1(struct rcu_head *node, void (*func)(str= uct rcu_head *node)) qemu_event_set(&rcu_call_ready_event); } =20 + +struct rcu_drain { + struct rcu_head rcu; + QemuEvent drain_complete_event; +}; + +static void drain_rcu_callback(struct rcu_head *node) +{ + struct rcu_drain *event =3D (struct rcu_drain *)node; + qemu_event_set(&event->drain_complete_event); +} + +/* + * This function ensures that all pending RCU callbacks + * on the current thread are done executing + + * drops big qemu lock during the wait to allow RCU thread + * to process the callbacks + * + */ + +void drain_call_rcu(void) +{ + struct rcu_drain rcu_drain; + bool locked =3D qemu_mutex_iothread_locked(); + + memset(&rcu_drain, 0, sizeof(struct rcu_drain)); + qemu_event_init(&rcu_drain.drain_complete_event, false); + + if (locked) { + qemu_mutex_unlock_iothread(); + } + + + /* + * RCU callbacks are invoked in the same order as in which they + * are registered, thus we can be sure that when 'drain_rcu_callback' + * is called, all RCU callbacks that were registered on this thread + * prior to calling this function are completed. + * + * Note that since we have only one global queue of the RCU callbacks, + * we also end up waiting for most of RCU callbacks that were register= ed + * on the other threads, but this is a side effect that shoudn't be + * assumed. + */ + + call_rcu1(&rcu_drain.rcu, drain_rcu_callback); + qemu_event_wait(&rcu_drain.drain_complete_event); + + if (locked) { + qemu_mutex_lock_iothread(); + } + +} + void rcu_register_thread(void) { assert(rcu_reader.ctr =3D=3D 0); --=20 2.26.2