[RFC PATCH v2 2/5] server: Add a new server request "notify_async_direct_result."
Jinoh Kang
jinoh.kang.kr at gmail.com
Thu Jan 27 13:13:48 CST 2022
On 1/28/22 04:05, Jinoh Kang wrote:
> Some I/O operations need a way to "queue" the async to the target object
> first, even if the operation itself is to be completed synchronously.
> After synchronous completion, it needs a way to notify the
> IO_STATUS_BLOCK values back to the server.
>
> Add a new wineserver request, "notify_async_direct_result", which
> notifies direct (i.e. synchronous) completion of async from the same
> thread.
>
> Signed-off-by: Jinoh Kang <jinoh.kang.kr at gmail.com>
> ---
>
> Notes:
> v1 -> v2: dequeue async after failed completion
>
> server/async.c | 84 ++++++++++++++++++++++++++++++++++++++++-----
> server/protocol.def | 10 ++++++
> 2 files changed, 86 insertions(+), 8 deletions(-)
>
> diff --git a/server/async.c b/server/async.c
> index 6373e8c1ae4..714e82362c6 100644
> --- a/server/async.c
> +++ b/server/async.c
> @@ -473,6 +473,17 @@ static void add_async_completion( struct async *async, apc_param_t cvalue, unsig
> if (async->completion) add_completion( async->completion, async->comp_key, cvalue, status, information );
> }
>
> +static void async_dequeue( struct async *async )
> +{
> + if (!async->queue) return;
> +
> + list_remove( &async->queue_entry );
> + async_reselect( async );
> + async->fd = NULL;
> + async->queue = NULL;
> + release_object( async );
> +}
> +
> /* store the result of the client-side async callback */
> void async_set_result( struct object *obj, unsigned int status, apc_param_t total )
> {
> @@ -531,14 +542,7 @@ void async_set_result( struct object *obj, unsigned int status, apc_param_t tota
> async->completion_callback( async->completion_callback_private );
> async->completion_callback = NULL;
>
> - if (async->queue)
> - {
> - list_remove( &async->queue_entry );
> - async_reselect( async );
> - async->fd = NULL;
> - async->queue = NULL;
> - release_object( async );
> - }
> + async_dequeue( async );
> }
> }
>
> @@ -750,3 +754,67 @@ DECL_HANDLER(get_async_result)
> }
> set_error( iosb->status );
> }
> +
> +/* Notify direct completion of async and close the wait handle */
> +DECL_HANDLER(notify_async_direct_result)
> +{
> + struct async *async = (struct async *)get_handle_obj( current->process, req->handle, 0, &async_ops );
> +
> + if (!async) return;
> +
> + if (async->iosb && async->unknown_status && !async->pending && async->terminated)
> + {
> + /* Reactivate async. We call async_reselect() later. */
> + async->terminated = 0;
> +
> + /* Set result for async_handoff(). */
> + set_error( req->status );
> + async->iosb->result = req->information;
> +
> + /* The async_handoff() call prior to the current server request was
> + * effectively a no-op since async->unknown_status is 1. Calling it
> + * again with async->unknown_status = 0 will do the remaining steps.
> + */
> + async->unknown_status = 0;
> + async_handoff( async, NULL, 0 );
> +
> + if (get_error() == STATUS_PENDING)
> + {
> + async_reselect( async );
> + }
> + else if (NT_ERROR( get_error() ))
> + {
> + /* synchronous I/O failure: don't invoke callbacks, only dequeue it. */
> + async_dequeue( async );
Note: we can't use async_set_result() here. async_handoff() leaves async->terminated as 0, and async_set_result() has "assert( async->terminated )".
Thus, reusing async_set_result() here requires either:
1. Setting async->pending to 0 so that async_handoff() will call async_terminate().
This is obviously incorrect since unwanted IOCP packets and APCs will fire on synchronous failure.
2. Not using async_handoff(). We have to copy a lot of code (particulary setting pending and direct_result flags) out of async_handoff() to do this.
> + }
> + else
> + {
> + /* I/O completed successfully. The client has already set the IOSB,
> + * so we can skip waiting on wait_handle and do async_set_result()
> + * directly.
> + *
> + * If !async->direct_result, an APC_ASYNC_IO has been fired.
> + * async_set_result() will be called when the APC returns.
> + */
> + if (async->direct_result)
> + {
> + async_set_result( &async->obj, async->iosb->status, async->iosb->result );
> + async->direct_result = 0;
> + }
> +
> + /* close wait handle here to avoid extra server round trip */
> + if (async->wait_handle)
> + {
> + close_handle( async->thread->process, async->wait_handle );
> + async->wait_handle = 0;
> + }
> + }
> +
> + /* The wait handle is preserved only when the status is STATUS_PENDING
> + * and async->blocking is set (i.e. we're going to block on it). */
> + reply->handle = async->wait_handle;
> + }
> + else set_error( STATUS_ACCESS_DENIED );
> +
> + release_object( &async->obj );
> +}
> diff --git a/server/protocol.def b/server/protocol.def
> index 02e73047f9b..2c3b8dbc619 100644
> --- a/server/protocol.def
> +++ b/server/protocol.def
> @@ -2163,6 +2163,16 @@ enum message_type
> @END
>
>
> +/* Notify direct completion of async and close the wait handle */
> + at REQ(notify_async_direct_result)
> + obj_handle_t handle; /* wait handle */
> + unsigned int status; /* completion status */
> + apc_param_t information; /* IO_STATUS_BLOCK Information */
> + at REPLY
> + obj_handle_t handle; /* wait handle, or NULL if closed */
> + at END
> +
> +
> /* Perform a read on a file object */
> @REQ(read)
> async_data_t async; /* async I/O parameters */
>
--
Sincerely,
Jinoh Kang
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