Hi,
I have a question about shared texture caches.
Basically, are these a “Good Thing” to use across threads?
If not, how “bad” is it?
We have a system whereby threads are created for jobs whenever they are needed
(it actually uses Qt’s Concurrent system).
Each thread can use the texture system, so I had it set to share the texture
cache across threads.
This is fine until you have a file that does not exist.
One thread will come along, try to open the file, fail, and mark it as broken
(this is all done when inside the get_texture_handle) which is correct.
Now, this thread is going to call texture() in a little while, but in the
meantime another thread is fired up as part of the job.
When this gets initialised, we create a new texture cache member pointer by
calling TextureSystem::create()
Inside here, because it’s marked as being shared, it will invalidate all files
in the cache.
Part of this invalidation means the broken flag is reset to false.
Now the other thread gets a look in, tries to use the file in the texture call,
and crashes because the broken flag is reset and it goes sailing through and
tries to access the 0th element in the subimage list (which obviously does not
exist!)
So, I’m wondering how I should best handle this situation.
Should I perhaps:
a) Not use a shared texture cach (this sounds like a bad thing to me)
b) Not create new texture cache pointers but to share the one globally over
threads - but how would I get the PerThreadInfo instances that I need?
c) Something else ….
Any thoughts or help on this would be greatly appreciated - I’m sure this must
be a very common scenario!
Best Regards,
Simon
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