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]> --- 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
