Subject: Re: [linux-audio-user] about 2.6.x woes [nptl?]
From: Jack O'Quin (joq_AT_io.com)
Date: Wed Jun 23 2004 - 20:13:14 EEST
Florian Schmidt <mista.tapas_AT_gmx.net> writes:
> well, i stumbled across this thread on the jackit-devel mailing list
> about trying to set LD_ASSUME_KERNEL=2.4.22 and run all jack stuff
> [server and clients with this env var set] and it worked
> wonders.. 2*512 works very nice again..
Yes, this works fine for me. I can even run 2.6.7 with realtime-lsm
at 2*32 (using a delta-66). It gets quite a few xruns at that
setting, but will run all night without crashing. This is as good I
get with 2.4-lowlat.
Fernando has observed additional problems on Fedora Core 2, which are
not fixed by setting this environment variable. He developed a JACK
patch to hack around some additional bugs in pthread_create(). These
have not yet been integrated into JACK CVS, but should be soon.
Because of these problems, CCRMA currently does not recommend using
FC2.
> i suspect this is nptl related (see the jackit-devel thread for
> details:
> http://sourceforge.net/mailarchive/message.php?msg_id=8629219).. i
> think the LD_ASSUME_KERNEL switch somehow makes ld.so link to another
> libc or something w/o nptl? anyone knows details?
Similar problems have been observed with 2.6 kernels even without
NPTL. The environment variable seems to force use of the 2.4-style
kernel interfaces, instead.
> so i just wanted to urge all the users of 2.6.x and who experience
> strange weird non rt operation with jack to try it. maybe it
> helps...
>
> i wrote myself a bash script called "realrealtime" and put that in my
> path:
>
> LD_ASSUME_KERNEL=2.4.22 $@
>
> and use that to start al my jack stuff :)
That works.
Or, you can just set it globally in your ~/.profile (or wherever you
choose to put things like that).
> Any ideas about why jackd behaves so weird in the first place
> appreciated..
I don't think anyone fully understands the problem, yet. It *seems*
to be somewhere in the interaction between the kernel and the pthreads
library.
-- joq
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