Yikes, not this again.... On Dec 15, 2009, at 11:42 AM, Olivier Guilyardi wrote: > On 12/15/2009 08:04 PM, Paul Davis wrote: >> 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. 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 And, until the jack ringbuffer gets fixed, the PortAudio ringbuffer appears safe for use on multiprocessor weakly-ordered systems. -Sean _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
