From patchwork Mon Feb 15 15:00:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 12088335 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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 0EB96C433E0 for ; Mon, 15 Feb 2021 15:11:00 +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 BBCB364DCF for ; Mon, 15 Feb 2021 15:10:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BBCB364DCF 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]:57244 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lBfWc-0006Yl-Uw for qemu-devel@archiver.kernel.org; Mon, 15 Feb 2021 10:10:58 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55404) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lBfNj-0005lY-9J for qemu-devel@nongnu.org; Mon, 15 Feb 2021 10:01:49 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23127) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lBfNR-0000qV-QX for qemu-devel@nongnu.org; Mon, 15 Feb 2021 10:01:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613401289; 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=LQuK7B1zQjPnR1Or4CfzlmST0ttXFEex4jpU9vIz9uE=; b=WhvJU2svNwIsrKNwauZXns5GTCZejar2+vFUHCPawQv3823a2YBUoPI3+jcK0NXcN/WIXd g8+1swcCVkUCXhmME1vgMRLJOStuKeNxK1EG1qH//wNDeCPR/92BuSM9zhPlrMVFjIS+TF qBFlradE2JCi+H5WP5DhJotM9YGPR3k= 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-51-DS_ofvzlNrWf9JP_HATm5w-1; Mon, 15 Feb 2021 10:01:25 -0500 X-MC-Unique: DS_ofvzlNrWf9JP_HATm5w-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 B8382107ACED; Mon, 15 Feb 2021 15:01:16 +0000 (UTC) Received: from merkur.fritz.box (ovpn-113-28.ams2.redhat.com [10.36.113.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id AB2A05C233; Mon, 15 Feb 2021 15:01:15 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 10/11] monitor: Fix assertion failure on shutdown Date: Mon, 15 Feb 2021 16:00:59 +0100 Message-Id: <20210215150100.436555-11-kwolf@redhat.com> In-Reply-To: <20210215150100.436555-1-kwolf@redhat.com> References: <20210215150100.436555-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H3=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: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Commit 357bda95 already tried to fix the order in monitor_cleanup() by moving shutdown of the dispatcher coroutine further to the start. However, it didn't go far enough: iothread_stop() makes sure that all pending work (bottom halves) in the AioContext of the monitor iothread is completed. iothread_destroy() depends on this and fails an assertion if there is still a pending BH. While the dispatcher coroutine is running, it will try to resume the monitor after taking a request out of the queue, which involves a BH. The dispatcher is run until it terminates in the AIO_WAIT_WHILE() loop. However, adding new BHs between iothread_stop() and iothread_destroy() is forbidden. Fix this by stopping the dispatcher first before shutting down the other parts of the monitor. This means we can now receive requests that aren't handled any more when QEMU is shutting down, but this is unlikely to be a problem for QMP clients. Fixes: 357bda9590784ff75803d52de43150d4107ed98e Signed-off-by: Kevin Wolf Message-Id: <20210212172028.288825-2-kwolf@redhat.com> Tested-by: Markus Armbruster Reviewed-by: Markus Armbruster Signed-off-by: Kevin Wolf --- monitor/monitor.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/monitor/monitor.c b/monitor/monitor.c index 1e4a6b3f20..e94f532cf5 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -618,16 +618,6 @@ void monitor_data_destroy(Monitor *mon) void monitor_cleanup(void) { - /* - * We need to explicitly stop the I/O thread (but not destroy it), - * clean up the monitor resources, then destroy the I/O thread since - * we need to unregister from chardev below in - * monitor_data_destroy(), and chardev is not thread-safe yet - */ - if (mon_iothread) { - iothread_stop(mon_iothread); - } - /* * The dispatcher needs to stop before destroying the monitor and * the I/O thread. @@ -637,6 +627,11 @@ void monitor_cleanup(void) * eventually terminates. qemu_aio_context is automatically * polled by calling AIO_WAIT_WHILE on it, but we must poll * iohandler_ctx manually. + * + * Letting the iothread continue while shutting down the dispatcher + * means that new requests may still be coming in. This is okay, + * we'll just leave them in the queue without sending a response + * and monitor_data_destroy() will free them. */ qmp_dispatcher_co_shutdown = true; if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) { @@ -647,6 +642,16 @@ void monitor_cleanup(void) (aio_poll(iohandler_get_aio_context(), false), qatomic_mb_read(&qmp_dispatcher_co_busy))); + /* + * We need to explicitly stop the I/O thread (but not destroy it), + * clean up the monitor resources, then destroy the I/O thread since + * we need to unregister from chardev below in + * monitor_data_destroy(), and chardev is not thread-safe yet + */ + if (mon_iothread) { + iothread_stop(mon_iothread); + } + /* Flush output buffers and destroy monitors */ qemu_mutex_lock(&monitor_lock); monitor_destroyed = true;