From nobody Thu Apr 17 12:37:15 2025
Delivered-To: importer@patchew.org
Received-SPF: temperror (zoho.com: Error in retrieving data from DNS)
client-ip=208.118.235.17;
envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org;
helo=lists.gnu.org;
Authentication-Results: mx.zohomail.com;
spf=temperror (zoho.com: Error in retrieving data from DNS)
smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org
Return-Path: <qemu-devel-bounces+importer=patchew.org@nongnu.org>
Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by
mx.zohomail.com
with SMTPS id 1513697342851892.0417318746154;
Tue, 19 Dec 2017 07:29:02 -0800 (PST)
Received: from localhost ([::1]:49395 helo=lists.gnu.org)
by lists.gnu.org with esmtp (Exim 4.71)
(envelope-from <qemu-devel-bounces+importer=patchew.org@nongnu.org>)
id 1eRJp3-0000vW-KK
for importer@patchew.org; Tue, 19 Dec 2017 10:28:49 -0500
Received: from eggs.gnu.org ([2001:4830:134:3::10]:58022)
by lists.gnu.org with esmtp (Exim 4.71)
(envelope-from <stefanha@redhat.com>) id 1eRJa7-000592-C7
for qemu-devel@nongnu.org; Tue, 19 Dec 2017 10:13:24 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
(envelope-from <stefanha@redhat.com>) id 1eRJa1-0007Iq-HS
for qemu-devel@nongnu.org; Tue, 19 Dec 2017 10:13:23 -0500
Received: from mx1.redhat.com ([209.132.183.28]:60912)
by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32)
(Exim 4.71) (envelope-from <stefanha@redhat.com>) id 1eRJa1-0007IC-Ai
for qemu-devel@nongnu.org; Tue, 19 Dec 2017 10:13:17 -0500
Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com
[10.5.11.15])
(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
(No client certificate requested)
by mx1.redhat.com (Postfix) with ESMTPS id 87753C0587CE;
Tue, 19 Dec 2017 15:13:16 +0000 (UTC)
Received: from localhost (ovpn-117-161.ams2.redhat.com [10.36.117.161])
by smtp.corp.redhat.com (Postfix) with ESMTP id 1B6D85EE11;
Tue, 19 Dec 2017 15:13:15 +0000 (UTC)
From: Stefan Hajnoczi <stefanha@redhat.com>
To: <qemu-devel@nongnu.org>
Date: Tue, 19 Dec 2017 15:11:39 +0000
Message-Id: <20171219151144.11120-19-stefanha@redhat.com>
In-Reply-To: <20171219151144.11120-1-stefanha@redhat.com>
References: <20171219151144.11120-1-stefanha@redhat.com>
X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16
(mx1.redhat.com [10.5.110.32]);
Tue, 19 Dec 2017 15:13:16 +0000 (UTC)
X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic]
[fuzzy]
X-Received-From: 209.132.183.28
Subject: [Qemu-devel] [PULL v2 18/23] block: avoid recursive AioContext
acquire in bdrv_inactivate_all()
X-BeenThere: qemu-devel@nongnu.org
X-Mailman-Version: 2.1.21
Precedence: list
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org
Sender: "Qemu-devel" <qemu-devel-bounces+importer=patchew.org@nongnu.org>
X-ZohoMail: RSF_6 Z_629925259 SPT_0
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
From: Paolo Bonzini <pbonzini@redhat.com>
BDRV_POLL_WHILE() does not support recursive AioContext locking. It
only releases the AioContext lock once regardless of how many times the
caller has acquired it. This results in a hang since the IOThread does
not make progress while the AioContext is still locked.
The following steps trigger the hang:
$ qemu-system-x86_64 -M accel=3Dkvm -m 1G -cpu host \
-object iothread,id=3Diothread0 \
-device virtio-scsi-pci,iothread=3Diothread0 \
-drive if=3Dnone,id=3Ddrive0,file=3Dtest.img,format=
=3Draw \
-device scsi-hd,drive=3Ddrive0 \
-drive if=3Dnone,id=3Ddrive1,file=3Dtest.img,format=
=3Draw \
-device scsi-hd,drive=3Ddrive1
$ qemu-system-x86_64 ...same options... \
-incoming tcp::1234
(qemu) migrate tcp:127.0.0.1:1234
...hang...
Tested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20171207201320.19284-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/block.c b/block.c
index 9a1a0d1e73..1c37ce4554 100644
--- a/block.c
+++ b/block.c
@@ -4320,9 +4320,15 @@ int bdrv_inactivate_all(void)
BdrvNextIterator it;
int ret =3D 0;
int pass;
+ GSList *aio_ctxs =3D NULL, *ctx;
=20
for (bs =3D bdrv_first(&it); bs; bs =3D bdrv_next(&it)) {
- aio_context_acquire(bdrv_get_aio_context(bs));
+ AioContext *aio_context =3D bdrv_get_aio_context(bs);
+
+ if (!g_slist_find(aio_ctxs, aio_context)) {
+ aio_ctxs =3D g_slist_prepend(aio_ctxs, aio_context);
+ aio_context_acquire(aio_context);
+ }
}
=20
/* We do two passes of inactivation. The first pass calls to drivers'
@@ -4340,9 +4346,11 @@ int bdrv_inactivate_all(void)
}
=20
out:
- for (bs =3D bdrv_first(&it); bs; bs =3D bdrv_next(&it)) {
- aio_context_release(bdrv_get_aio_context(bs));
+ for (ctx =3D aio_ctxs; ctx !=3D NULL; ctx =3D ctx->next) {
+ AioContext *aio_context =3D ctx->data;
+ aio_context_release(aio_context);
}
+ g_slist_free(aio_ctxs);
=20
return ret;
}
--=20
2.14.3