Messages in this thread | | | Date | Fri, 14 Oct 2005 07:56:05 -0700 | From | Mark Knecht <> | Subject | Re: 2.6.14-rc4-rt1 - enable IRQ-off tracing causes kernel to fault at boot |
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On 10/13/05, Ingo Molnar <mingo@elte.hu> wrote: > > * Mark Knecht <markknecht@gmail.com> 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 > by -rt1. > > 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]
Indeed it is fixed by doing this. Options are on but the modified kernel does boot:
***************************************************************************** * * * REMINDER, the following debugging options are turned on in your .config: * * * * CONFIG_DEBUG_PREEMPT * * CONFIG_CRITICAL_PREEMPT_TIMING * * CONFIG_CRITICAL_IRQSOFF_TIMING * * * * they may increase runtime overhead and latencies. * * * *****************************************************************************
mark@lightning ~ $ uname -a Linux lightning 2.6.14-rc4-rt1 #8 PREEMPT Fri Oct 14 07:46:29 PDT 2005 x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux mark@lightning ~ $
> > (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. > > Ingo >
Will got back to the original entry.S file with the IRQoff option turned off. Let me know when you have a fix to test, or if you need more data.
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