Re: [PATCH 4/8] udp_vu: Make virtqueue buffers stack-local for thread safety

On Tue, Jun 16, 2026 at 07:10:48PM +0200, Laurent Vivier wrote:

The function-local static buffers elem[] and iov_vu[] in udp_vu_sock_to_tap() are shared across all threads. When multiple worker threads process UDP vhost-user data concurrently, they would stomp on each other's buffers.

Remove the static qualifier so each call gets its own stack-allocated arrays, eliminating cross-thread sharing.

Signed-off-by: Laurent Vivier

Reviewed-by: David Gibson I generally dislike static locals anyway, though they have their uses. I'd be happy to see this applied independent of the rest of the series.

--- udp_vu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/udp_vu.c b/udp_vu.c index 864e7a99b8d9..342673dc7e6d 100644 --- a/udp_vu.c +++ b/udp_vu.c @@ -146,8 +146,8 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx, { const struct flowside *toside = flowside_at_sidx(tosidx); bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)); - static struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; - static struct iovec iov_vu[VIRTQUEUE_MAX_SIZE]; + struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; + struct iovec iov_vu[VIRTQUEUE_MAX_SIZE];

Nit, this needs a little re-ordering to preserve the reverse christmas tree.

int rx_queue = QPAIR_TOGUEST_QUEUE(qpair); struct vu_dev *vdev = c->vdev; struct vu_virtq *vq = &vdev->vq[rx_queue]; -- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson