From mboxrd@z Thu Jan 1 00:00:00 1970 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=-9.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 11DF9C4363A for ; Fri, 23 Oct 2020 14:19:04 +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 407C221527 for ; Fri, 23 Oct 2020 14:19:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AQlhv1Vu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 407C221527 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]:41580 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kVxuI-0003IA-0Y for qemu-devel@archiver.kernel.org; Fri, 23 Oct 2020 10:19:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39564) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kVxtb-0002o9-9u for qemu-devel@nongnu.org; Fri, 23 Oct 2020 10:18:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40411) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kVxtY-0008V5-KH for qemu-devel@nongnu.org; Fri, 23 Oct 2020 10:18:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603462696; 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: in-reply-to:in-reply-to:references:references; bh=3mg8CTFvXVMDZHyjaOTkZVEFCEf9snkyLfDQ4Hjorcg=; b=AQlhv1VuU4MpPi55Mgruuk+OYovDcns/9nnoPl0NGwRQLp8Si5gfd7y4CC/v95pHEmpnEu luqOFx6XUChVUzF1ttpcghScT0RIg5falWJU1DY505MKDBnVBVzUQg2tp7w7IwhTjEZLeT 2YFmmwuz2WPc/xr8trycORprRoOQ+Jc= 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-1-p0Gmd8_ZN4OoT3LXx-mNww-1; Fri, 23 Oct 2020 10:18:12 -0400 X-MC-Unique: p0Gmd8_ZN4OoT3LXx-mNww-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 02DF4804B6A; Fri, 23 Oct 2020 14:18:11 +0000 (UTC) Received: from merkur.fritz.box (ovpn-113-206.ams2.redhat.com [10.36.113.206]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DCAEB27BB4; Fri, 23 Oct 2020 14:18:06 +0000 (UTC) Date: Fri, 23 Oct 2020 16:18:05 +0200 From: Kevin Wolf To: Greg Kurz Subject: Re: [PATCH] block: End quiescent sections when a BDS is deleted Message-ID: <20201023141805.GE4793@merkur.fritz.box> References: <160344969243.4091343.14371338409686732879.stgit@bahia.lan> MIME-Version: 1.0 In-Reply-To: <160344969243.4091343.14371338409686732879.stgit@bahia.lan> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/23 01:44:00 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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: Stefan Hajnoczi , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 23.10.2020 um 12:41 hat Greg Kurz geschrieben: > 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) I think the name should make clear that this is meant as a counterpart for bdrv_drain_all_begin(), so maybe bdrv_drain_all_end_quiesce()? (The function is not suitable for any other kinds of drain because the parameters it passes to bdrv_do_drained_end() are only the same as for bdrv_drain_all_begin().) > +{ > + int drained_end_counter = 0; > + > + g_assert_cmpint(bs->quiesce_counter, >, 0); > + g_assert_cmpint(bs->refcnt, ==, 0); By the way, I didn't know about the problem with these macros either. > + 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); But here in the test case we should keep g_assert_cmpint() because it gives better error messages when it fails (and checkpatch doesn't warn about it in tests). Apart from the naming and checkpatch, this looks good to me. Kevin