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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 A9B08C388F9 for ; Fri, 23 Oct 2020 14:47:11 +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 1D2E52192A for ; Fri, 23 Oct 2020 14:47:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1D2E52192A 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+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38372 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kVyLW-0007UM-2V for qemu-devel@archiver.kernel.org; Fri, 23 Oct 2020 10:47:10 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46754) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kVyJs-0006Tp-NF; Fri, 23 Oct 2020 10:45:28 -0400 Received: from smtpout1.mo529.mail-out.ovh.net ([178.32.125.2]:33347) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kVyJp-0003hE-SI; Fri, 23 Oct 2020 10:45:28 -0400 Received: from mxplan5.mail.ovh.net (unknown [10.108.16.8]) by mo529.mail-out.ovh.net (Postfix) with ESMTPS id 2ED6068287F1; Fri, 23 Oct 2020 16:45:22 +0200 (CEST) Received: from kaod.org (37.59.142.99) by DAG8EX1.mxp5.local (172.16.2.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2044.4; Fri, 23 Oct 2020 16:45:21 +0200 Authentication-Results: garm.ovh; auth=pass (GARM-99G003b929e85f-4402-4332-95fa-088b3f1d6103, C0BA1F4BE5C42AD64430581CA289E8EEBB8A5892) smtp.auth=groug@kaod.org Date: Fri, 23 Oct 2020 16:45:20 +0200 From: Greg Kurz To: Kevin Wolf Subject: Re: [PATCH] block: End quiescent sections when a BDS is deleted Message-ID: <20201023164520.7a7211f7@bahia.lan> In-Reply-To: <20201023141805.GE4793@merkur.fritz.box> References: <160344969243.4091343.14371338409686732879.stgit@bahia.lan> <20201023141805.GE4793@merkur.fritz.box> X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [37.59.142.99] X-ClientProxiedBy: DAG1EX1.mxp5.local (172.16.2.1) To DAG8EX1.mxp5.local (172.16.2.71) X-Ovh-Tracer-GUID: 251dec91-46b9-48b7-8d31-b466678c1385 X-Ovh-Tracer-Id: 17041902465231788451 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedujedrkedtgdektdcutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvuffkjghfofggtgfgihesthejredtredtvdenucfhrhhomhepifhrvghgucfmuhhriicuoehgrhhouhhgsehkrghougdrohhrgheqnecuggftrfgrthhtvghrnhepvdefgfdtgeeluddujeejleffgffhhedtieeggffguddvgfekvefgfeettdejheevnecuffhomhgrihhnpehrvgguhhgrthdrtghomhenucfkpheptddrtddrtddrtddpfeejrdehledrudegvddrleelnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmohguvgepshhmthhpqdhouhhtpdhhvghlohepmhigphhlrghnhedrmhgrihhlrdhovhhhrdhnvghtpdhinhgvtheptddrtddrtddrtddpmhgrihhlfhhrohhmpehgrhhouhhgsehkrghougdrohhrghdprhgtphhtthhopehsthgvfhgrnhhhrgesrhgvughhrghtrdgtohhm Received-SPF: pass client-ip=178.32.125.2; envelope-from=groug@kaod.org; helo=smtpout1.mo529.mail-out.ovh.net X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/23 10:45:22 X-ACL-Warn: Detected OS = Linux 3.11 and newer X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-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" On Fri, 23 Oct 2020 16:18:05 +0200 Kevin Wolf wrote: > 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()? > Sure. > (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). > Sure, it makes sense to keep them in tests. The limitation only applies to the core code. > Apart from the naming and checkpatch, this looks good to me. > Cool, I'll send a v2 shortly. > Kevin >