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From f1ae5247cd1de4374905421e105d371aea6d7c75 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Wed, 5 Mar 2014 14:15:03 +0100
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Subject: [PATCH 01/16] dataplane: Fix startup race.
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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Message-id: <1394028903-5087-1-git-send-email-stefanha@redhat.com>
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Patchwork-id: 58018
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O-Subject: [RHEL7 qemu-kvm PATCH] dataplane: Fix startup race.
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Bugzilla: 1069541
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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From: Cornelia Huck <cornelia.huck@de.ibm.com>
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Bugzilla: 1069541
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Upstream: 8caf907f07688972e5e7cd11526079b1665d6dba
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BREW: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=7144761
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Avoid trying to setup dataplane again if dataplane setup is already in
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progress. This may happen if an eventfd is triggered during setup.
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I saw this occasionally with an experimental s390 irqfd implementation:
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virtio_blk_handle_output
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-> virtio_blk_data_plane_start
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-> virtio_ccw_set_host_notifier
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...
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-> virtio_queue_set_host_notifier_fd_handler
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-> virtio_queue_host_notifier_read
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-> virtio_queue_notify_vq
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-> virtio_blk_handle_output
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-> virtio_blk_data_plane_start
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-> vring_setup
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-> hostmem_init
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-> memory_listener_register
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-> BOOM
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As virtio-ccw tries to follow what virtio-pci does, it might be triggerable
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for other platforms as well.
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Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 8caf907f07688972e5e7cd11526079b1665d6dba)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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[----] : patches are identical
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[####] : number of functional differences between upstream/downstream patch
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[down] : patch is downstream-only
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The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
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001/1:[----] [-C] 'dataplane: Fix startup race.'
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 hw/block/dataplane/virtio-blk.c | 9 +++++++++
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 1 file changed, 9 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/block/dataplane/virtio-blk.c |    9 +++++++++
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 1 files changed, 9 insertions(+), 0 deletions(-)
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diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
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index 411becc..0b002ba 100644
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--- a/hw/block/dataplane/virtio-blk.c
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+++ b/hw/block/dataplane/virtio-blk.c
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@@ -42,6 +42,7 @@ typedef struct {
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 struct VirtIOBlockDataPlane {
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     bool started;
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+    bool starting;
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     bool stopping;
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     QEMUBH *start_bh;
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     QemuThread thread;
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@@ -464,8 +465,15 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
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         return;
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     }
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+    if (s->starting) {
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+        return;
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+    }
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+
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+    s->starting = true;
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+
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     vq = virtio_get_queue(s->vdev, 0);
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     if (!vring_setup(&s->vring, s->vdev, 0)) {
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+        s->starting = false;
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         return;
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     }
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@@ -495,6 +503,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
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     s->io_notifier = *ioq_get_notifier(&s->ioqueue);
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     aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io, flush_io);
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+    s->starting = false;
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     s->started = true;
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     trace_virtio_blk_data_plane_start(s);
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-- 
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1.7.1
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