Subject: [linux-audio-user] Re: Can low-latency patch cause CPU freeze?
From: Fernando Pablo Lopez-Lezcano (nando_AT_ccrma.stanford.edu)
Date: Fri Oct 26 2001 - 07:11:26 EEST
> I've installed a 2.4 kernel with low latency patches by downloading the
> Planet CCRMA rpms.
>
> Since then, I've noticed that after a period of time after bootup, I get
> a hard freeze in X - Neither Ctrl-alt-BS nor Ctrl-alt-del does anything,
> and the mouse cursor dissapeears. I don't have an other terminal handy
> to check if I can log in through a serial port. But I'm pretty sure it's
> hardware related because when this happens, the computer does not boot
> up for a period of time, giving the sequence of long beeps like a RAM
> error.
Could you count the beeps? And note the sequence? (I think it's two
different lenghts making up the pattern). Sometime ago I saw a web page
with the beep patterns and the corresponding errors, at least that would
pinpoint the culprit.
> I suspect that given the pattern over time, I have an overheating
> problem somewhere, and was wondering if anyone can think of any reason
> that the low-latency patches could contribute to this. I'm not
> suspecting the patches right way, because this could easily be
> coincidence, but I'd thought I'd ask just in case for some strange
> reason that patches could make the CPU run hotter. Actually, what comes
> to my mind is that possibly the patches cause the cpu to enter an idle
> loop instead of halting when idle, and this is enough to overwhelm my
> CPU fan.
Strange. Do you see anything at all in the logs after getting the machine
up and running again? (I suspect not). Does the problem go away if you
reboot into the old kernel? What version of XFree are you running? What
video card?
I can't think of a reason why the ll patch could be related to (potential)
overheating. One possibility is that the original redhat kernel had some
patch that made things work for your hardware configuration (and that is
not present in the Planet CCRMA kernel). I'm currently transitioning to a
new kernel (2.4.12-ac5 + low latency, much more reasonable VM performance
than 2.4.8, specially for machines with RAM<128M) that I have not yet
propagated to the Planet CCRMA software pages, maybe you would like to try
that one out.
> swapping hardware, I thought I'd ask just in case. In the mean time, I
> will experiment by disabling the patch (echo "0" > /proc/lowlatency) to
> see if it make a difference.
I'd try to boot into the old kernel and see if the problem goes away.
-- Fernando
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