From patchwork Tue Feb 13 17:34:27 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 10217265 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id EDF8660467 for ; Tue, 13 Feb 2018 18:21:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DFE0F28EFA for ; Tue, 13 Feb 2018 18:21:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D4D6628F19; Tue, 13 Feb 2018 18:21:18 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 6701728ED7 for ; Tue, 13 Feb 2018 18:21:18 +0000 (UTC) Received: from localhost ([::1]:59708 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1elfCf-0002E1-Ea for patchwork-qemu-devel@patchwork.kernel.org; Tue, 13 Feb 2018 13:21:17 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36303) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eleTe-0002Fl-E9 for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eleTc-0003C7-KD for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:46 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51834 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 1eleTc-0003Bu-GB for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:44 -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 1F472EB6F9; Tue, 13 Feb 2018 17:34:44 +0000 (UTC) Received: from localhost (ovpn-117-252.ams2.redhat.com [10.36.117.252]) by smtp.corp.redhat.com (Postfix) with ESMTP id C20F12024CA2; Tue, 13 Feb 2018 17:34:43 +0000 (UTC) From: Stefan Hajnoczi To: Date: Tue, 13 Feb 2018 17:34:27 +0000 Message-Id: <20180213173429.19501-4-stefanha@redhat.com> In-Reply-To: <20180213173429.19501-1-stefanha@redhat.com> References: <20180213173429.19501-1-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 [10.11.55.1]); Tue, 13 Feb 2018 17:34:44 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Tue, 13 Feb 2018 17:34:44 +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] [PATCH 3/5] 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: Kevin Wolf , Paolo Bonzini , Stefan Hajnoczi , Peter Maydell Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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) == 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) main_loop(); replay_disable_events(); + + /* The ordering of the following is delicate. Stop vcpus to prevent new + * 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 IOThreads + * (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(); /* vhost-user must be cleaned up before chardevs. */