From owner-freebsd-current@FreeBSD.ORG  Sat Jan 24 11:48:15 2004
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From: Stefan Ehmann <shoesoft@gmx.net>
To: Mathew Kanner <mat@cnd.mcgill.ca>
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Date: Sat, 24 Jan 2004 20:48:22 +0100
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cc: current@freebsd.org
Subject: Re: write(2) lc_r problem
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On Sat, 2004-01-24 at 20:15, Mathew Kanner wrote:
> On Jan 24, Stefan Ehmann wrote:
> > I'm trying to write a small sound application and run across a problem
> > on CURRENT.
> > 
> > It's very basic at the moment. It simply reads pcm data from a file and
> > uses write(2) on /dev/dsp.
> > 
> > But as soon as I link the program with -lc_r there's always about 1
> > second delay before a write call - which makes it pretty unusable for
> > playing sound.
> > 
> > It should be easy reproducable if you link audio/waveplay with -lc_r.
> > 
> > This doesn't happen in either FreeBSD 4.9, Knoppix or CURRENT if linked
> > with -lkse or -lthr.
> > 
> > Am I'm missing something basic when using write together with lc_r or
> > ist this a bug in CURRENT?
> 
> 	There is definetly a bug with the sound code when using vchans
> and select.  Make sure that  (using sysctl)
> 
> 	hw.snd.maxautovchans=0
> 	hw.snd.pcmX.vchans=0

You're right, that fixed it. That's also the reason why it worked on
stable (vchans was disabled there).