[ quesa-Bugs-902992 ] Make API re-entrant for multithreading

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Bugs item #902992, was opened at 2004-02-23 21:12
Message generated for change (Tracker Item Submitted) made by Item Submitter
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Dair Grant (grantd)
Assigned to: Nobody/Anonymous (nobody)
Summary: Make API re-entrant for multithreading

Initial Comment:
Discussion on the list about making the API re-entrant - logging 
here as a feature 
request.

-dair

*****

James Dessart wrote:

Is there a list somewhere of what Quesa functions are, or are not,  
reentrant?  It'd be nice to be able to push some of the more  
compute-bound functions out into multi-processor threads on the 
Mac  OS, in our application.

*****

Dair Grant wrote:

At present nothing is officially re-entrant - there aren't any locks 
whatsoever. In practice you would probably find that the math 
routines are probably safe, although even they should really have 
some protection in their glue around the global error state (or 
make the error state thread specific).


Doing a first pass on thread safety (i.e., one global lock which was 
acquired/released by every entry point) would be fairly easy since 
it could be munged into the glue code.

Allowing multiple threads inside Quesa at once would be more 
complex, although you could probably get most of the way there 
by having per-object locks since most routines pass the object 
they're working on around.

There is only bit of global data, so protecting that+the objects the 
current thread is working on would probably be enough (assuming 
a thread safe C library/OpenGL).


I suppose it depends on what the performance gains of doing that 
wold be vs the complexity of the extra locks.

My guess is it'd only really be worth it for things like the math 
routines, where you might want to dump transforming an array of 
vertices off to another thread?

*****

James Dessart wrote:

It's pretty much just the math routines, and perhaps setting  
TriMesh data.  Essentially, playing around with coordinates and  
such, without any rendering.

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