Re: [Dri-devel] Combined vblank-waiting and buffer swapping

[Ian R. <id...@us...>]

Mike Mestnik wrote:
> --- Ian Romanick <id...@us...> wrote:
> 
>>Basically, queuing commands while we wait for a swap to complete is like 
>>building a display list.  Maybe it would be easier to tackle the problem 
>>from that point of view?  When a swap is pending we'd "somehow" switch 
>>to build-display list mode.  When the swap completed we'd execute the 
>>currently built display list and switch back to immediate mode.  Dunno...
> 
> This sounds alot like something I would have done, could the pending commands be compiled,
> optimized, or compresed?  Also we can use an irq/signal(I.E. kill -WINCH) or an alarm to get back
> into client side code, can't we?  I don't know what WINCH is for but by default it's ignored.

I don't think we can use signals for a number of reasons.  Even though 
WINCH (or any other signal, for that matter) are unused by default, an 
application *can* use them for whatever it wants.  We don't want to 
steal signals from the application or vice versa.  I think there are 
things that we would need to do to submit buffered commands that can't 
be done from within a signal handler.

There *might* be some trickery that we could do with an extra thread, 
but that seems dangerous and error prone.