[linux-audio-dev] mutex in process callback?

[Lukas Degener]

>
>
>if i understand what you're asking correctly, you could just stash a
>copy of the current pointer at the start of the process callback. then
>(assuming there is only one pointer), the operation is atomic with
>respect to the process callback: either it happens before you get the
>copy of the pointer or not at all (since your copy of the pointer
>won't be updated until the next time the callback is run). 
>
Ah... you're right. Actualy this is pretty much straight forward.
Funny i didn't think of it myself :-)

There's one thing however, i am not completly sure about:
What happens if the working thread swaps buffers two times within one 
cycle of the
playback thread? I'll try to do a simple diagram:

                (Time) ---->

Playback 
----------------------------------------------------------------------------------------------> 
bang!
                front==A ... 
reading.....................................................still 
reading from A

Worker 
----------------------------------------------------->Worker------------------------------> 
bang!
               back==B, ...working on B...done...swap               
back==A!...working on A

May not be a very common situation, but who knows. So i would have to 
assure that
the worker thread does not process more than one "job" during one 
playback cycle.
Or use more than two buffers.
Or did i miss something here?

>if more
>than one pointer is involved stick the sets into arrays and stash the
>index to the current set instead of the pointers themselves. 
>
This will propably not be the case. At least i think so right now.

>hopefully that makes sense and is applicable.
>
It is indeed. I will try it.

Ah... another reply just droped into my mailbox <beep!> ... let's see 
what Paul suggests. :-)

Thanks  Rob,

Lukas