>>> this was discussed at some considerable length on jack-devel last >>> year, IIRC. >>> for single reader/single writer ringbuffers, i believe that we >>> concluded that memory barriers are not necessary. >> >> No, to me the conclusion was: we can't programmatically prove that >> memory >> barriers are needed (even on the most vulnerable architectures), >> but the theory >> say that they are, and they should be added for correctness. > > My understanding matches Olivier's. Intel processors have strong memory > ordering, and so on them the jack ringbuffer is safe without memory > barriers. However, some PPC processors, and SPARC V9s under linux > (but not > Solaris), use weak memory ordering, and on them, the jack ringbuffer > code > can theoretically fail.
exactly, the issue may not appear on x86, because of its memory consistency, weakly-ordered machines will need some barriers ... > See the "ring buffer memory barriers" discussion on jack-devel back in > October of last year for more information; in particular, this article > by Paul E. McKenney is very helpful: > > http://www.linuxjournal.com/article/8211 memory-barriers.txt of the linux kernel documentation is interesting as well ... cheers, tim -- [email protected] http://tim.klingt.org Contrary to general belief, an artist is never ahead of his time but most people are far behind theirs. Edgar Varèse
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