Sorry for being slow to respond...
On 1/27/22 22:17, Jinoh Kang wrote:
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:
- 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.
- 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.
Maybe just merge both branches (error/success) and force async_terminate() before calling async_set_result()?
Actually, I believe the right thing to do is just to set async->terminated = 1. In fact, I believe you should set async->terminated = 1 in the recv_socket request,
Yes, it's already done in async_handoff(). Note the precondition above:
- if (async->iosb && async->unknown_status && !async->pending && async->terminated)
- {
/* Reactivate async. We call async_reselect() later. */async->terminated = 0;otherwise async_waiting() will return 1 and the server will end up spinning and/or trying to wake the async. (Granted, that could be protected against by checking unknown_status, but...)
There are a few different ways to look at this, but one way (and what I think makes the most sense to me) is that we're completing the async as if it had been alerted, much as we would from a kernel APC, except that we're also setting the initial status, which wasn't known yet. Hence we want to go through async_set_result().
Along these lines, if you also set async->alerted = 1, you get the STATUS_PENDING "restart the wait" behaviour for free. Which makes conceptual sense as well.
I'm honestly split off as to which side should take the responsibility of setting "async->alerted = 1", async_handoff() or notify_async_direct_result. I suppose I'm going with the former, since that's where STATUS_ALERTED is received.
I think that inasmuch as we're mimicking the usual "alerted" code path, it makes conceptual sense to set async->alerted = 1 in async_handoff().
But then, shall the latter have "assert( async->alerted );"...?
Well, you can't do that, exactly, because we can't crash no matter what input we get from the client. But you could check for async->alerted and return STATUS_INVALID_PARAMETER or something if it's not set.
I suppose this is why you mentioned direct_result in [1]—i.e. we could just async_terminate(STATUS_ALERTED) in recv_socket. I can see both approaches working, but I think that open-coding the relevant parts of async_terminate would be better than trying to get direct_result manipulation exactly right.
I agree. I hope we don't also have to also open code "async_handoff()", though.
Of course, I also haven't tried...
[1] https://www.winehq.org/pipermail/wine-devel/2022-January/205774.html
That said, the more I work with the async code, the more I learn to hate all those status bitfields... I think it's much better off merging as many states as possible into a single enum, so that the lifecycle is explicit (e.g. ASYNC_INITIAL -> ASYNC_QUEUED -> ASYNC_ALERTED -> ...) (I'm aware it was much worse before that, making the status field serve the dual role of async state and I/O status.)
Sure, I think that's something worth looking into.