[linux-audio-user] cannot write to jackstart sync pipe 4 (Bad file descriptor)

Rui Nuno Capela rncbc at rncbc.org
Fri Nov 4 14:07:05 EST 2005

Florian Schmidt wrote:
> On Fri, 04 Nov 2005 12:48:22 -0500
> Peter Lutek <plutek at infinity.net> wrote:
>>>>  The subject of this message is the output of qjackctl when I launch  
>>>> jackd  with :
>>>>       /usr/bin/jackd -R -dalsa -dhw:0 -r44100 -p256 -n2
>>> Weird. jackstart should only ever be used when you tell qjackctl to do
>>> it. See the setup tab -> server path. Make sure it's just "jackd" there.
>> dunno about carlos, but mine is set to "jackd" -- i still get the error. 
>> note that jackd IS starting fine, but we ALSO get the jackstart sync 
>> pipe error message. yeah... it's wierd.
> maybe it's a qjackctl bug. hmm.. 


IMO this error is pretty innocuous. It is only issued if jackd is built 
with ./configure --enable-capabilities, which does not make sense 
anymore for the 2.6 kernel line.

Apparentely the error is due to some mishap with the pipe file 
descriptors that the jackstart launcher proccess uses to communicate 
with the actual jackd process. Which are simply not used if you don't 
use jackstart. However, jackd still tries to access the pipe if built 
with capabilities enabled.

Maybe, it only happens when you tell qjackctl to capture the jackd 
standard output into its own messages window, and those pipe/file 
descriptors get loose (because it is assumed to be file descriptors 
number 4 and 5, coincidentally right after the standard ones).

Just a though. Not sure.
rncbc aka Rui Nuno Capela
rncbc at rncbc.org

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