On Thu, Mar 12, 2026 at 1:05 AM Chaohai Chen <[email protected]> wrote: > > KCSAN warns as follow: > > [ 109.277250] > ================================================================== > [ 109.283600] BUG: KCSAN: data-race in > virtqueue_enable_cb_delayed_split+0x10f/0x170 > > [ 109.295263] race at unknown origin, with read to 0xffff8b2a92ef2042 of 2 > bytes by interrupt on cpu 1: > [ 109.306934] virtqueue_enable_cb_delayed_split+0x10f/0x170 > [ 109.312880] virtqueue_enable_cb_delayed+0x3b/0x70 > [ 109.318852] start_xmit+0x315/0x860 [virtio_net] > [ 109.324532] dev_hard_start_xmit+0x85/0x380 > [ 109.329993] sch_direct_xmit+0xd3/0x680 > [ 109.335360] __dev_xmit_skb+0x4ee/0xcc0 > [ 109.340568] __dev_queue_xmit+0x560/0xe00 > [ 109.345701] ip_finish_output2+0x49a/0x9b0 > [ 109.350743] __ip_finish_output+0x131/0x250 > [ 109.355789] ip_finish_output+0x28/0x180 > [ 109.360712] ip_output+0xa0/0x1c0 > [ 109.365479] __ip_queue_xmit+0x68d/0x9e0 > [ 109.370156] ip_queue_xmit+0x33/0x40 > [ 109.374783] __tcp_transmit_skb+0x1703/0x1970 > [ 109.379467] __tcp_send_ack.part.0+0x1bb/0x320 > ... > [ 109.499585] do_idle+0x7a/0xe0 > [ 109.502979] cpu_startup_entry+0x25/0x30 > [ 109.506481] start_secondary+0x116/0x150 > [ 109.509930] common_startup_64+0x13e/0x141 > > [ 109.516626] value changed: 0x0029 -> 0x002a > ================================================================================ > > Add READ_ONCE() to fix the warning. > > Signed-off-by: Chaohai Chen <[email protected]>
Nit: maybe it's better to explain it's a false positive. Acked-by: Jason Wang <[email protected]> Thanks > --- > drivers/virtio/virtio_ring.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 335692d41617..ceb026161639 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1112,8 +1112,9 @@ static bool virtqueue_enable_cb_delayed_split(struct > vring_virtqueue *vq) > &vring_used_event(&vq->split.vring), > cpu_to_virtio16(vq->vq.vdev, vq->last_used_idx + > bufs)); > > - if (unlikely((u16)(virtio16_to_cpu(vq->vq.vdev, > vq->split.vring.used->idx) > - - vq->last_used_idx) > bufs)) { > + if (unlikely((u16)(virtio16_to_cpu(vq->vq.vdev, > + READ_ONCE(vq->split.vring.used->idx)) > + - vq->last_used_idx) > bufs)) { > END_USE(vq); > return false; > } > -- > 2.43.0 >
