Subject: Re: [linux-audio-dev] Lock Free Ringbuffer in C ?
From: David Olofson (david_AT_olofson.net)
Date: Sat Apr 05 2003 - 21:36:33 EEST
On Friday 04 April 2003 17.15, torbenh_AT_gmx.de wrote:
> On Fri, Apr 04, 2003 at 12:47:28PM +0200, David Olofson wrote:
> > On Thursday 03 April 2003 15.36, torbenh_AT_gmx.de wrote:
> > > i remember i have read a statement about a lock free ringbuffer
> > > implemented in C somewhere.
> > >
> > > Can anybody remeber it ?
> >
> > Here's one in C; the 'sfifo':
> >
> > http://olofson.net/mixed.html
> >
> >
> > I've been using it in various environments for a few years, but
> > that doesn't guarantee anything. ;-)
>
> well... it should for such small code :)
You might think so, but I'm not NASA. ;-)
As an example, the crash bug when specifying non-power-of-two buffer
size had been there for years before I found it, simply because it
took that long before anyone tried to ask for something like 4000
bytes.
Testing does not guarantee anything beyond the specific conditions you
test, under the exact conditions of your tests.
> but how do i handle this sensibly ?
>
>
> res = sfifo_write(sf, &buf, j);
> if(res != j)
> {
> printf("Write failed!\n");
>
> // eeek... no i dont want that...
> sleep(1);
> } else if(res)
> printf("Wrote %d\n", res);
write() can only fail if you forgot to initialize the fifo before
using it, or possibly if someone stomped the fifo struct. In the case
of the latter, you have more serious things to worry about! :-)
Feel free to ignore the return value from write() - unless it's valid
for your writer to mess with closed fifos. (I wouldn't recommend
doing that with statically allocated fifo structs, since you'd have
to make sure to initialize them anyway.)
//David Olofson - Programmer, Composer, Open Source Advocate
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