linuxaudio.org

Paul Davis wrote:

quoted text
> 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

quoted text
>> 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

quoted text
>> 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

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