Re: [Qemu-devel] [PATCH v2 07/11] aio-posix: introduce aio_{disable, enable}_clients

[Stefan Hajnoczi]

On Wed, Jul 29, 2015 at 12:42:10PM +0800, Fam Zheng wrote:
> +void aio_disable_enable_clients(AioContext *ctx, int clients_mask,
> +                                bool is_disable)
> +{
> +    AioHandler *node;
> +    aio_context_acquire(ctx);
> +
> +    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
> +        if (!node->deleted && node->type & clients_mask) {
> +            node->disable_cnt += is_disable ? 1 : -1;
> +        }
> +    }
> +    aio_context_release(ctx);
> +}

If someone adds an fd of a disabled type *after* the call to
aio_disable_clients() then it won't be disabled.

Another approach is to keep an array of counters per AioContext and
check the counters during aio_poll() when deciding which fds to monitor.

Also, this function acquires/releases AioContext so it's worth
mentioning in the doc comments that this function is thread-safe.