Re: [RFC 3/3] virtio-gpu: make the IO handler reentrant

[Michael Tokarev]

02.09.2020 19:22, Li Qiang wrote:
..
> @@ -809,6 +809,10 @@ void virtio_gpu_process_cmdq(VirtIOGPU *g)
>  {
>      struct virtio_gpu_ctrl_command *cmd;
>  
> +    if (atomic_read(&g->in_io)) {
> +        return;
> +    }
> +    atomic_set(&g->in_io, 1);

Can't we race in these two instructions? Both
threads atomic_reads at the same time, both see zero,
and both are trying to set it to 1, no?

Just asking really, b/c despite of the atomic_ prefix,
to me this look a bit unsafe..

Thanks,

/mjt