When booting a Qemu VM with virtio-blk and KCSAN enabled, KCSAN emits the following warning about a data-race in vring_interrupt().
================================================================== BUG: KCSAN: data-race in vring_interrupt+0x125/0x1f0 race at unknown origin, with read to 0xffff88810218d942 of 2 bytes by interrupt on cpu 7: vring_interrupt+0x125/0x1f0 __handle_irq_event_percpu+0xaf/0x310 handle_irq_event+0x76/0xf0 handle_edge_irq+0x1fc/0x3e0 __common_interrupt+0x79/0x160 common_interrupt+0xa6/0xe0 asm_common_interrupt+0x26/0x40 pv_native_safe_halt+0x17/0x20 default_idle+0x9/0x10 default_idle_call+0x3c/0x110 do_idle+0x166/0x190 cpu_startup_entry+0x29/0x30 start_secondary+0x114/0x140 common_startup_64+0x129/0x138 value changed: 0x3a3a -> 0x3a3b Reported by Kernel Concurrency Sanitizer on: CPU: 7 UID: 0 PID: 0 Comm: swapper/7 Not tainted 6.19.0-rc7+ #223 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-9.fc43 06/10/2025 ================================================================== This warning is likely a false positive as the change happens on the virtio vring. Annotate the return of more_used() with data_race() to silence the warning. Signed-off-by: Johannes Thumshirn <[email protected]> --- drivers/virtio/virtio_ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index d1033768b6cd..7fa8f2ebe94e 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -2695,7 +2695,7 @@ irqreturn_t vring_interrupt(int irq, void *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); - if (!more_used(vq)) { + if (data_race(!more_used(vq))) { pr_debug("virtqueue interrupt with no work for %p\n", vq); return IRQ_NONE; } -- 2.52.0
