From nobody Wed Oct 22 13:01:18 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) 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=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1520434173419935.7468724221133; Wed, 7 Mar 2018 06:49:33 -0800 (PST) Received: from localhost ([::1]:33846 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1etaNj-0000OF-8z for importer@patchew.org; Wed, 07 Mar 2018 09:49:27 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53126) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1etaH2-0002sr-O2 for qemu-devel@nongnu.org; Wed, 07 Mar 2018 09:42:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1etaH1-0005JJ-Mr for qemu-devel@nongnu.org; Wed, 07 Mar 2018 09:42:32 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50878 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1etaGu-00058T-JT; Wed, 07 Mar 2018 09:42:24 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2217A4000787; Wed, 7 Mar 2018 14:42:24 +0000 (UTC) Received: from localhost (ovpn-116-116.ams2.redhat.com [10.36.116.116]) by smtp.corp.redhat.com (Postfix) with ESMTP id 56BAB7C42; Wed, 7 Mar 2018 14:42:17 +0000 (UTC) From: Stefan Hajnoczi To: Date: Wed, 7 Mar 2018 14:42:04 +0000 Message-Id: <20180307144205.20619-4-stefanha@redhat.com> In-Reply-To: <20180307144205.20619-1-stefanha@redhat.com> References: <20180307144205.20619-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 07 Mar 2018 14:42:24 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 07 Mar 2018 14:42:24 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'stefanha@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH v3 3/4] virtio-scsi: fix race between .ioeventfd_stop() and vq handler X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , qemu-block@nongnu.org, Peter Crosthwaite , "Michael S. Tsirkin" , Max Reitz , Stefan Hajnoczi , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" If the main loop thread invokes .ioeventfd_stop() just as the vq handler function begins in the IOThread then the handler may lose the race for the AioContext lock. By the time the vq handler is able to acquire the AioContext lock the ioeventfd has already been removed and the handler isn't supposed to run anymore! Use the new aio_wait_bh_oneshot() function to perform ioeventfd removal from within the IOThread. This way no races with the vq handler are possible. Signed-off-by: Stefan Hajnoczi --- hw/scsi/virtio-scsi-dataplane.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplan= e.c index 1c33322ba6..912e5005d8 100644 --- a/hw/scsi/virtio-scsi-dataplane.c +++ b/hw/scsi/virtio-scsi-dataplane.c @@ -107,9 +107,10 @@ static int virtio_scsi_vring_init(VirtIOSCSI *s, VirtQ= ueue *vq, int n, return 0; } =20 -/* assumes s->ctx held */ -static void virtio_scsi_clear_aio(VirtIOSCSI *s) +/* Context: BH in IOThread */ +static void virtio_scsi_dataplane_stop_bh(void *opaque) { + VirtIOSCSI *s =3D opaque; VirtIOSCSICommon *vs =3D VIRTIO_SCSI_COMMON(s); int i; =20 @@ -171,7 +172,7 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev) return 0; =20 fail_vrings: - virtio_scsi_clear_aio(s); + aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s); aio_context_release(s->ctx); for (i =3D 0; i < vs->conf.num_queues + 2; i++) { virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false); @@ -207,7 +208,7 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev) s->dataplane_stopping =3D true; =20 aio_context_acquire(s->ctx); - virtio_scsi_clear_aio(s); + aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s); aio_context_release(s->ctx); =20 blk_drain_all(); /* ensure there are no in-flight requests */ --=20 2.14.3