From patchwork Fri Oct 23 10:41:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 11852727 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 25F376A2 for ; Fri, 23 Oct 2020 10:44:52 +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 8CE5E20FC3 for ; Fri, 23 Oct 2020 10:44:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8CE5E20FC3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:44268 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kVuZ0-0005u4-GV for patchwork-qemu-devel@patchwork.kernel.org; Fri, 23 Oct 2020 06:44:50 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44216) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kVuWO-0004eb-0w for qemu-devel@nongnu.org; Fri, 23 Oct 2020 06:42:09 -0400 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:39445) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kVuWK-0003tm-Fk for qemu-devel@nongnu.org; Fri, 23 Oct 2020 06:42:05 -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-74-kFnqikVFNqu4hdg0g-AdDw-1; Fri, 23 Oct 2020 06:41:41 -0400 X-MC-Unique: kFnqikVFNqu4hdg0g-AdDw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A27F6804B6E; Fri, 23 Oct 2020 10:41:40 +0000 (UTC) Received: from bahia.lan (ovpn-115-53.ams2.redhat.com [10.36.115.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 68B3E10013D7; Fri, 23 Oct 2020 10:41:33 +0000 (UTC) Subject: [PATCH] block: End quiescent sections when a BDS is deleted From: Greg Kurz To: qemu-devel@nongnu.org Date: Fri, 23 Oct 2020 12:41:32 +0200 Message-ID: <160344969243.4091343.14371338409686732879.stgit@bahia.lan> User-Agent: StGit/0.21 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=groug@kaod.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Received-SPF: softfail client-ip=205.139.111.44; envelope-from=groug@kaod.org; helo=us-smtp-delivery-44.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/23 06:41:46 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -11 X-Spam_score: -1.2 X-Spam_bar: - X-Spam_report: (-1.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_SOFTFAIL=0.665 autolearn=no 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: Kevin Wolf , Stefan Hajnoczi , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" If a BDS gets deleted during blk_drain_all(), it might miss a call to bdrv_do_drained_end(). This means missing a call to aio_enable_external() and the AIO context remains disabled for ever. This can cause a device to become irresponsive and to disrupt the guest execution, ie. hang, loop forever or worse. This scenario is quite easy to encounter with virtio-scsi on POWER when punching multiple blockdev-create QMP commands while the guest is booting and it is still running the SLOF firmware. This happens because SLOF disables/re-enables PCI devices multiple times via IO/MEM/MASTER bits of PCI_COMMAND register after the initial probe/feature negotiation, as it tends to work with a single device at a time at various stages like probing and running block/network bootloaders without doing a full reset in-between. This naturally generates many dataplane stops and starts, and thus many drain sections that can race with blockdev_create_run(). In the end, SLOF bails out. It is somehow reproducible on x86 but it requires to generate articial dataplane start/stop activity with stop/cont QMP commands. In this case, seabios ends up looping for ever, waiting for the virtio-scsi device to send a response to a command it never received. Add a helper that pairs all previously called bdrv_do_drained_begin() with a bdrv_do_drained_end() and call it from bdrv_close(). While at it, update the "/bdrv-drain/graph-change/drain_all" test in test-bdrv-drain so that it can catch the issue. BugId: https://bugzilla.redhat.com/show_bug.cgi?id=1874441 Signed-off-by: Greg Kurz --- block.c | 9 +++++++++ block/io.c | 13 +++++++++++++ include/block/block.h | 6 ++++++ tests/test-bdrv-drain.c | 1 + 4 files changed, 29 insertions(+) diff --git a/block.c b/block.c index 430edf79bb10..ddcb36dd48a8 100644 --- a/block.c +++ b/block.c @@ -4458,6 +4458,15 @@ static void bdrv_close(BlockDriverState *bs) } QLIST_INIT(&bs->aio_notifiers); bdrv_drained_end(bs); + + /* + * If we're still inside some bdrv_drain_all_begin()/end() sections, end + * them now since this BDS won't exist anymore when bdrv_drain_all_end() + * gets called. + */ + if (bs->quiesce_counter) { + bdrv_drained_end_quiesce(bs); + } } void bdrv_close_all(void) diff --git a/block/io.c b/block/io.c index 54f0968aee27..8a0da06bbb14 100644 --- a/block/io.c +++ b/block/io.c @@ -633,6 +633,19 @@ void bdrv_drain_all_begin(void) } } +void bdrv_drained_end_quiesce(BlockDriverState *bs) +{ + int drained_end_counter = 0; + + g_assert_cmpint(bs->quiesce_counter, >, 0); + g_assert_cmpint(bs->refcnt, ==, 0); + + while (bs->quiesce_counter) { + bdrv_do_drained_end(bs, false, NULL, true, &drained_end_counter); + } + BDRV_POLL_WHILE(bs, qatomic_read(&drained_end_counter) > 0); +} + void bdrv_drain_all_end(void) { BlockDriverState *bs = NULL; diff --git a/include/block/block.h b/include/block/block.h index d16c401cb44e..c0ce6e690081 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -779,6 +779,12 @@ void bdrv_drained_end(BlockDriverState *bs); */ void bdrv_drained_end_no_poll(BlockDriverState *bs, int *drained_end_counter); +/** + * End all quiescent sections started by bdrv_drain_all_begin(). This is + * only needed when deleting a BDS before bdrv_drain_all_end() is called. + */ +void bdrv_drained_end_quiesce(BlockDriverState *bs); + /** * End a quiescent section started by bdrv_subtree_drained_begin(). */ diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c index 1595bbc92e9e..8a29e33e004a 100644 --- a/tests/test-bdrv-drain.c +++ b/tests/test-bdrv-drain.c @@ -594,6 +594,7 @@ static void test_graph_change_drain_all(void) g_assert_cmpint(bs_b->quiesce_counter, ==, 0); g_assert_cmpint(b_s->drain_count, ==, 0); + g_assert_cmpint(qemu_get_aio_context()->external_disable_cnt, ==, 0); bdrv_unref(bs_b); blk_unref(blk_b);