Re: bug report/suggested temp. patch: handling bursts of sent keys

[Jon TURNEY <jon dot turney at dronecode dot org dot uk>]

On 13/02/2010 20:24, Mark Lillibridge wrote:
> Jon wrote:
> >   Thanks for the patch.  Have you actually tested that this resolves your problem?
>
>      Yes.  Of course, really, really large bursts will still fail, but
> they should be very rare.

Perhaps you might try the attached patch, instead, and see if that helps.

> >   On 23/01/2010 22:02, Mark Lillibridge wrote:
> >   >       I am not a Windows programmer.  Can someone tell me if it's okay for
> >   >  winWindowProc to block?  In particular, could we make it block until the
> >   >  mieq queue is not full?
> >
> >   I think blocking would just result in a deadlock, as the X server is only
> >   single-threaded.  The windows message pump is called when the server has no
> >   other work to do.
> >
> >   This should be documented in [1], although perhaps that is lacking in detail.
> >
> > I notice that winWakeHandler()/winBlockHandler() try to completely empty the
> > windows message queue, which leads to this problem as the server won't get a
> > chance to process anything (draining the mieq queue) until they return.
> >
> > It might be enough to resolve this problem to allow those functions to
> > complete after processing a limited number of events (chosen so as to not
> > overflow the mieq queue), or if they notice that the event queue has crossed
> > some high-water mark threshold.
>
>      This is an interesting idea; I spent a while looking at
> WaitFor.c/WaitForSomething, but it's pretty opaque -- couldn't figure
> out when/under what conditions winWakeHandler is called by it.  E.g.,
> what's the actual priority between emptying the queue and processing
> window messages?

Let's see: right at the end of hw/xwin/InitInput.c we open "/dev/windows" (a 
special device which becomes ready when there is anything on the windows 
message queue) and add that to the select mask.  When the select returns, all 
the wakeup handlers are run, including winWakeHandler() which checks the WM 
message queue.

--
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

Attachment: 0001-Process-one-Windows-message-per-wakeup-rather-than-a.patch
Description: application/itunes-itlp

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