Commit 8caf907f authored by Cornelia Huck's avatar Cornelia Huck Committed by Stefan Hajnoczi
Browse files

dataplane: Fix startup race.



Avoid trying to setup dataplane again if dataplane setup is already in
progress. This may happen if an eventfd is triggered during setup.

I saw this occasionally with an experimental s390 irqfd implementation:

virtio_blk_handle_output
-> virtio_blk_data_plane_start
-> virtio_ccw_set_host_notifier
...
-> virtio_queue_set_host_notifier_fd_handler
-> virtio_queue_host_notifier_read
-> virtio_queue_notify_vq
-> virtio_blk_handle_output
-> virtio_blk_data_plane_start
-> vring_setup
-> hostmem_init
-> memory_listener_register
-> BOOM

As virtio-ccw tries to follow what virtio-pci does, it might be triggerable
for other platforms as well.
Signed-off-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 5daa74a6
......@@ -42,6 +42,7 @@ typedef struct {
struct VirtIOBlockDataPlane {
bool started;
bool starting;
bool stopping;
QEMUBH *start_bh;
QemuThread thread;
......@@ -451,8 +452,15 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
return;
}
if (s->starting) {
return;
}
s->starting = true;
vq = virtio_get_queue(s->vdev, 0);
if (!vring_setup(&s->vring, s->vdev, 0)) {
s->starting = false;
return;
}
......@@ -482,6 +490,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
s->io_notifier = *ioq_get_notifier(&s->ioqueue);
aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io);
s->starting = false;
s->started = true;
trace_virtio_blk_data_plane_start(s);
......
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