Paul Davis wrote: > On Wed, 2008-10-15 at 13:02 +0200, Olivier Guilyardi wrote: >> >> I'm no memory barrier expert, but from what I read this looks like a complex >> topic. Adding them to jack's ring buffer may be hazardous without carefully >> crafted test cases. Bugs related to missing barriers may or may not happen >> according to various hardware-related issues. > > the point of memory barriers is really to remove the need for test > cases :) I meant Test First, not putting a memory barrier between us and past bugs ;) My concern is: people around say memory barriers are missing, but could anyone write a unit test that actually turns this assumption into a bug? >> Here's what Ross Bencina says about it: "the correct implementation of these >> algorithms also requires an understanding of the use of memory barriers to force >> the order of some memory reads and writes on SMP systems. This is because memory >> controllers may reorder reads and writes as observed by other processors on an >> SMP system (or by prehipherals on a uniprocessor system)." > > what is complex about memory barriers is understanding *why* they are > necessary. their use is really quite straightforward. Yeah, I saw that. In Portaudio, they consist in 3 lines in the whole ringbuffer code. But as Miles Davis (sort of) said, playing a few notes might involve a great expertise. >> As a user of these projects I sense that people from Portaudio, PulseAudio and >> Jack could collaborate on this topic. And Ross Bencina's initiative may be the >> right place for this: >> http://www.audiomulch.com/~rossb/code/lockfree/liblfds/index.htm > > if you read that page carefully you will see that ross was still waiting > to set up a repository when that page was last updated (2006). a shame. > though i can speak, did i do anything to help it out? I didn't see that the page was so old.. I just saw there was "some" activity on the mailing list (http://tech.groups.yahoo.com/group/liblf-dev/). I'll try to find some time to work on a patch or a new lib, but I can't promise it will happen soon. PS: I forwarded this thread to Ross -- Olivier Guilyardi / Samalyse _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user