[RFC PATCH v4 2/5] server: Add a new server request "notify_async_direct_result."

[Jinoh Kang]

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
    v2 -> v3: rewrite handling of pending/failed asyncs.
    v3 -> v4:
    - add assert( async->iosb );
    - make robust against abrupt transition/cancellation:
      don't return STATUS_ACCESS_DENIED on precondition failure
      (client won't know what to do with STATUS_ACCESS_DENIED anyway)
    - always return wait_handle if possible
    - clarify and rearrange comments

 server/async.c      | 62 +++++++++++++++++++++++++++++++++++++++++++++
 server/protocol.def | 10 ++++++++
 2 files changed, 72 insertions(+)

diff --git a/server/async.c b/server/async.c
index e169bb23225..8852ff1c6d5 100644
--- a/server/async.c
+++ b/server/async.c
@@ -752,3 +752,65 @@ DECL_HANDLER(get_async_result)
     }
     set_error( iosb->status );
 }
+
+/* Notify direct completion of async and close the wait handle if not blocking */
+DECL_HANDLER(notify_async_direct_result)
+{
+    struct async *async = (struct async *)get_handle_obj( current->process, req->handle, 0, &async_ops );
+
+    if (!async) return;
+
+    /* we only return an async handle for asyncs created via create_request_async() */
+    assert( async->iosb );
+
+    if (async->unknown_status && !async->pending &&
+        async->terminated && async->alerted &&
+        async->iosb->status == STATUS_PENDING)
+    {
+        /* async->terminated is 1, so async_terminate() won't do anything.
+         * We need to set the status and result for ourselves.
+         */
+        async->iosb->status = req->status;
+        async->iosb->result = req->information;
+
+        /* Set status for async_handoff(). */
+        set_error( async->iosb->status );
+
+        /* 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.
+         *
+         * NOTE: async_handoff() is being called with async->terminated = 1.
+         */
+        async->unknown_status = 0;
+        async_handoff( async, NULL, 0 );
+
+        /* If the I/O has completed successfully, the client would have already
+         * set the IOSB. Therefore, we can skip waiting on wait_handle and do
+         * async_set_result() directly.
+         */
+        async_set_result( &async->obj, async->iosb->status, async->iosb->result );
+
+        /* Close wait handle here to avoid extra server round trip if the I/O
+         * has completed successfully.
+         *
+         * - If STATUS_PENDING, async_handoff() decides whether to close
+         *   the wait handle for us.  The wait handle is kept open if
+         *   async->blocking is set (i.e. we're going to block on it).
+         *
+         * - If failed (NT_ERROR), async_handoff() always closes
+         *   the wait_handle, which means async->wait_handle == 0.
+         */
+        if (async->wait_handle && async->iosb->status != STATUS_PENDING)
+        {
+            close_handle( async->thread->process, async->wait_handle );
+            async->wait_handle = 0;
+        }
+    } /* Otherwise, async have been abruptly transitioned (cancelled?). */
+
+    /* async_set_result() may have overriden the error value.  Reset it. */
+    set_error( async->iosb->status );
+    reply->handle = async->wait_handle;
+
+    release_object( &async->obj );
+}
diff --git a/server/protocol.def b/server/protocol.def
index 02e73047f9b..d79eca074a0 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 if not blocking */
+ 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 */
-- 
2.34.1