From nobody Wed Dec 17 05:38:23 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1518687849454477.4274215582391; Thu, 15 Feb 2018 01:44:09 -0800 (PST) Received: from localhost ([::1]:55302 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emG5D-00039t-Ka for importer@patchew.org; Thu, 15 Feb 2018 04:44:03 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35295) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emG3Z-0001zn-D6 for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emG3Y-00007L-El for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:21 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47096 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1emG3T-00005o-MQ; Thu, 15 Feb 2018 04:42:15 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 39097402290A; Thu, 15 Feb 2018 09:42:15 +0000 (UTC) Received: from localhost (ovpn-116-159.ams2.redhat.com [10.36.116.159]) by smtp.corp.redhat.com (Postfix) with ESMTP id D9FA02024CA8; Thu, 15 Feb 2018 09:42:14 +0000 (UTC) From: Stefan Hajnoczi To: Date: Thu, 15 Feb 2018 09:42:08 +0000 Message-Id: <20180215094210.27770-2-stefanha@redhat.com> In-Reply-To: <20180215094210.27770-1-stefanha@redhat.com> References: <20180215094210.27770-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Thu, 15 Feb 2018 09:42:15 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Thu, 15 Feb 2018 09:42:15 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'stefanha@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PULL v2 1/3] vl: pause vcpus before stopping iothreads X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Stefan Hajnoczi , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") introduced iothread_stop_all() to avoid the following virtio-scsi assertion failure: assert(blk_get_aio_context(d->conf.blk) =3D=3D s->ctx); Back then the assertion failed because when bdrv_close_all() made d->conf.blk NULL, blk_get_aio_context() returned the global AioContext instead of s->ctx. The same assertion can still fail today when vcpus submit new I/O requests after iothread_stop_all() has moved the BDS to the global AioContext. This patch hardens the iothread_stop_all() approach by pausing vcpus before calling iothread_stop_all(). Note that the assertion failure is a race condition. It is not possible to reproduce it reliably. Signed-off-by: Stefan Hajnoczi Message-id: 20180201110708.8080-1-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi --- vl.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/vl.c b/vl.c index 21878496ec..7a5554bc41 100644 --- a/vl.c +++ b/vl.c @@ -4767,10 +4767,18 @@ int main(int argc, char **argv, char **envp) =20 main_loop(); replay_disable_events(); + + /* The ordering of the following is delicate. Stop vcpus to prevent n= ew + * I/O requests being queued by the guest. Then stop IOThreads (this + * includes a drain operation and completes all request processing). = At + * this point emulated devices are still associated with their IOThrea= ds + * (if any) but no longer have any work to do. Only then can we close + * block devices safely because we know there is no more I/O coming. + */ + pause_all_vcpus(); iothread_stop_all(); - - pause_all_vcpus(); bdrv_close_all(); + res_free(); =20 /* vhost-user must be cleaned up before chardevs. */ --=20 2.14.3