Re: [LAD] Patching linux 2.6.26.3

Robin Gareus wrote:
> Rui Nuno Capela wrote:
>> Robin Gareus wrote:
>>> Rui Nuno Capela wrote:
>>>> Tim Goetze wrote:
>>>>> [Tim Goetze]
>>>>>
>>>>>> [victor]
>>>>>>> I was told to revert to 2.6.24.17 (not possible in my specific
>>>>>>> case, but there you go), in this list. Or to join the tuner's list.
>>>>>> http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.26.3-rt2.bz2
>>>>>>
>>>>>>
>>>>>> worked for me. Applied cleanly and compiled well after turning off
>>>>>> some RCU-related preemption options that caused compilation errors,
>>>>>> but I was in no mood to find out the exact how and why. So far, it
>>>>>> has collected a few hours of solid uptime too, but I haven't done
>>>>>> any latency measuring.
>>>>> Update: on my laptop, the patched 2.6.26.3 kernel boots into an
>>>>> endless list of tracebacks on the console. On the main box, USB
>>>>> MIDI input is only read as soon as a key is pressed on the USB
>>>>> keyboard (the one with the letters, not the MIDI one ...). USB MIDI
>>>>> out is broken, too. So it's back to the old version.
>>>>>
>>>> ah, it seems i'm not alone.
>>> hehe , nice try. We won't let you go that easily ;)
>>>
>>>> i'm currently recovering myself from schock after returning from
>>>> vacation and while trying 2.6.26.x-rt for the rentrýe it all seemed
>>>> to work fine except omg... midi timing is a wreck, specially wrt.alsa
>>>> sequencer. event delivery is completely fubar. i mean, completely.
>>>> true showstopper, whatever :(
>>>> cacophony seems to be the right word to express what it is.
>>>> however, didn't had the time to check whether NOHZ is at stake. i'm
>>>> certainly going back to 2.6.25.x-rt where things are still sane and
>>>> pleasant for a while.
>>>> btw, having NOHZ=y (aka tickless kernel) has been the norm here,
>>>> since its inception
>>> CONFIG_NO_HZ=y - same norm here; with good results iff it works.
>>>
>> just tested 2.6.23.3-rt3 here with NO_HZ not set in my (old) pentium4
>> desktop.
>
>> it just confirmed that NO_HZ is not the culprit here. midi events are
>> still being delivered *completely* out of time and the funny thing is it
>> just gets somewhat better whenever you hit the pc-keyboard keys.
>> however, it all gets back to badness once you stop pressing any key (eg.
>> shift-key)
>
>> another funny thing goes that on a core2 duo T7200 laptop (x86_64) the
>> same kernel config it runs all fine (NO_HZ=y)
>
>
> http://kerneltrap.org/Linux/Removing_the_Big_Kernel_Lock mentions TTY
> drivers being a problem, actually "a long and difficult task"..
>

ah. and more fun to the party: if the pc-keyboard is abused in way above
said, to let midi delivery work miserably, it just stops working at all.
you'll end with a dead pc-keyboard, something like its key-buffer gets
fed up and can't get drained anymore.

seeya

-- 
rncbc aka Rui Nuno Capela
rncbc@rncbc.org
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