3 Apr
2003
3 Apr
'03
9:06 a.m.
i remember i have read a statement about a lock free ringbuffer
implemented in C somewhere.
Can anybody remeber it ?
--
torben Hohn
http://galan.sourceforge.net -- The graphical Audio language
3 Apr
3 Apr
9:12 a.m.
On Thu, Apr 03, 2003 at 03:36:32PM +0200, torbenh(a)gmx.de wrote:
i remember i have read a statement about a lock free ringbuffer
implemented in C somewhere.
courtesy of paul davis:
you should use a lock free ringbuffer. we will be adding example code
to the example-clients directory soon. existing code is in ardour's
source base (for C++). the example code will be in
example-clients/capture_client.c.
where ardour is ardour.sf.net. (i doubt there is anything hugely non-C in
the ringbuffer code proper).
rob
----
Robert Melby
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!gt4255a
Internet: async(a)cc.gatech.edu
4 Apr
4 Apr
7:57 a.m.
On Thursday 03 April 2003 15.36, torbenh(a)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. ;-)
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`-----------------------------------> http://audiality.org -'
--- http://olofson.net --- http://www.reologica.se ---
8:50 a.m.
On Fri, Apr 04, 2003 at 12:47:28PM +0200, David Olofson wrote:
On Thursday 03 April 2003 15.36, torbenh(a)gmx.de
wrote:
well... it should for such small code :)
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);
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. ;-)
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`-----------------------------------> http://audiality.org -'
--- http://olofson.net --- http://www.reologica.se ---
--
torben Hohn
http://galan.sourceforge.net -- The graphical Audio language
9:46 a.m.
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...
there are several solutions, none of them particularly good. the best
is to wait on a FIFO. these provide a fast, 99% non-blocking way to
get 1 process to wake up another. the "real" solution needs to be
provided by the kernel, and futexes in 2.5/2.6 will be fairly
close. they are still not completely correct for our purposes, but
they will probably work OK.
--p
5 Apr
5 Apr
11:09 a.m.
On Fri, Apr 04, 2003 at 07:43:40AM -0500, Paul Davis wrote:
there are several solutions, none of them particularly
good. the best
is to wait on a FIFO. these provide a fast, 99% non-blocking way to
get 1 process to wake up another. the "real" solution needs to be
provided by the kernel, and futexes in 2.5/2.6 will be fairly
close. they are still not completely correct for our purposes, but
they will probably work OK.
The futexes are the solution. You can basically wait, until a
long at a specified address is changed, if you tell the kernel
that it might be changed, after you did. So the kernel just does
the sleep/wakeup for you, nothing else.
But you can also just do what you want and use the NPTL of RH9,
which uses futexes transparently, if available.
That way you get a performance gain on machines you recommend
while still being correct on every other machine with POSIX
threading implemented.
Regards
Ingo Oeser
--
Marketing ist die Kunst, Leuten Sachen zu verkaufen, die sie
nicht brauchen, mit Geld, was sie nicht haben, um Leute zu
beeindrucken, die sie nicht moegen.
3:46 p.m.
On Friday 04 April 2003 17.15, torbenh(a)gmx.de wrote:
On Fri, Apr 04, 2003 at 12:47:28PM +0200, David
Olofson wrote:
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.
On Thursday 03 April 2003 15.36, torbenh(a)gmx.de
wrote:
well... it should for such small code :) 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. ;-) 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
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`-----------------------------------> http://audiality.org -'
--- http://olofson.net --- http://www.reologica.se ---
3:54 p.m.
On Friday 04 April 2003 17.15, torbenh(a)gmx.de wrote:
[...]
res = sfifo_write(sf, &buf, j);
if(res != j)
{
DOH! Sorry, I'm in a hurry and misread your code.
Well, we're talking about a basic lock free FIFO here, based on atomic
reads and writes of two indices. Proper blocking read() and write()
would require talking to the OS scheduler one way or another (block +
wake up functionality), and that's not even possible on some of the
platforms this code is used on.
That said, I do have a version with busy-waiting versions, meant for
use with IRQs in environments without threads. I wouldn't recommend
using this on any multitasking OS, though, except possibly for IPC
across CPUs in SMP systems in some special cases.
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`-----------------------------------> http://audiality.org -'
--- http://olofson.net --- http://www.reologica.se ---
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linux-audio-dev@lists.linuxaudio.org
8 comments
6 participants
participants (6)
-
David Olofson -
Ingo Oeser -
Paul Davis -
rm -
torbenh＠gmx.de -
Vincent Touquet