On Wed, Nov 29, 2017 at 10:49:49PM +0800, Fam Zheng wrote:
> diff --git a/util/async.c b/util/async.c
> index 4dd9d95a9e..cca0efd263 100644
> --- a/util/async.c
> +++ b/util/async.c
> @@ -402,6 +402,7 @@ AioContext *aio_context_new(Error **errp)
> AioContext *ctx;
>
> ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
> + QTAILQ_INIT(&ctx->drain_ops);
> aio_context_setup(ctx);
>
> ret = event_notifier_init(&ctx->notifier, false);
> @@ -506,3 +507,75 @@ void aio_context_release(AioContext *ctx)
> {
> qemu_rec_mutex_unlock(&ctx->lock);
> }
> +
> +/* Called with ctx->lock */
> +void aio_context_drained_begin(AioContext *ctx)
> +{
> + AioDrainOps *ops;
> +
> + /* TODO: When all external fds are handled in the following drain_ops
> + * callbacks, aio_disable_external can be dropped. */
> + aio_disable_external(ctx);
> +restart:
> + ctx->drain_ops_updated = false;
> + QTAILQ_FOREACH(ops, &ctx->drain_ops, next) {
> + ops->drained_begin(ops->opaque);
> + if (ctx->drain_ops_updated) {
> + goto restart;
drained_begin() can be called multiple times. This needs to be clearly
documented to avoid surprises.
> + }
> + }
> +}
> +
> +/* Called with ctx->lock */
> +void aio_context_drained_end(AioContext *ctx)
> +{
> + AioDrainOps *ops;
> +
> +restart:
> + ctx->drain_ops_updated = false;
> + QTAILQ_FOREACH(ops, &ctx->drain_ops, next) {
> + if (ops->is_new) {
> + continue;
> + }
> + ops->drained_end(ops->opaque);
drained_end() can be called multiple times. This needs to be clearly
documented to avoid surprises.
> + if (ctx->drain_ops_updated) {
> + goto restart;
> + }
> + }
> + if (aio_enable_external(ctx)) {
> + QTAILQ_FOREACH(ops, &ctx->drain_ops, next) {
> + ops->is_new = false;
> + }
> + }
This is weird, aio_context_drained_end() has nesting support for
->is_new but not for ->drained_end() calls. I'm not sure where you're
going with these semantics yet.
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