[Pixman] Making ref counting thread safe
sandmann at daimi.au.dk
Thu Dec 23 19:05:07 PST 2010
Christian Hergert <christian.hergert at gmail.com> writes:
> If I where to go through and work on making the reference counting
> thread safe, what things would I need to make sure I take into
> account for the patch to be accepted? For example:
I put up some notes on the subject here:
Basically, the only two types of systems that really matter is Windows
On Windows we always have atomic primitives available through the
Interlocked* functions. On pthreads, we can statically initialize
mutexes, so if worst comes to worst, we can fake the atomics with
> * Do we just need to use __sync_fetch_and_add()/__sync_sub_and_fetch()
> within the functions?
I think they should be hidden behind PIXMAN_ATOMIC_* macros.
> * Should we abstract the atomic operations to support compilers other
> than GCC? If so, what compilers do we need to support?
With the approach described in the link above, I think it should be
possible to support most compilers without too much trouble.
> * Do we wan't to fallback to ++/-- when used under X since threading
> isn't needed? (Add something like pixman_thread_init()).
Wouldn't any such mechanism have overhead in itself? In any case, I
don't think this would be necessary until benchmarks say otherwise.
> * Is it okay to start with just pixman_image_t and support others
> in future patches?
I think that's fine.
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