Re: 2.6.14-rc4-rt1 - enable IRQ-off tracing causes kernel to fault at boot
From: Ingo Molnar
Date: Thu Oct 13 2005 - 22:56:10 EST
* Mark Knecht <markknecht@xxxxxxxxx> wrote:
> Ingo & Steve,
> Thank you for your great instructions that even a guitar player
> could basically follow. After about an hour of messing around I did
> manage to capture the crash. The console file is attached.
> NOTE: The first time I booted the kernel it got to the crash point and
> the machine rebooted. The second time it booted I got the trace. Both
> boots are in the capture file.
thanks, this log is much more informative. No smoking gun though, but it
seems something fundamental (probably lowlevel x64 code) has been broken
Do the crashes go away if you take the -rc3-rt13 version of
arch/x86_64/kernel/entry.S and copy it over into the -rc4-rt1 tree?
[this undoes a particular set of CONFIG_CRITICAL_IRQSOFF_TIMING fixes
from the x64 code, which i did during -rc3-rt13 => -rc4-rt1]
(Note that doing this will re-introduce tracing bugs, which can result
in false-positive latency readings - but it should fix any related
lowlevel bug in the assembly code.)
if this indeed solves the crash then i'd suggest to restore the -rt1
version of entry.S, and i'd suggest to disable CRITICAL_IRQSOFF_TIMING
until i fix it. You should be able to get pretty good latency tracing
info even without CRITICAL_IRQSOFF_TIMING.
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