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    SubjectRe: Race condition in module load causing undefined symbols
    K.R. Foley wrote:
    > Steve Lord wrote:
    >
    >> Andrew Morton wrote:
    >>
    >>> Stephen Lord <lord@xfs.org> wrote:
    >>>
    >>>> Pozsár Balázs wrote:
    >>>> > On Sat, Jun 11, 2005 at 08:23:20AM -0500, Steve Lord wrote:
    >>>> > >>I think this is not actually module loading itself, but a problem
    >>>> >>between the fork/exec/wait code in nash and the kernel.
    >>>> > > > I do not use nash, only bash, so this is not a nash-specific
    >>>> issue.
    >>>> > >
    >>>> I disabled hyperthreading and things started working, so are there any
    >>>> HT related scheduling bugs right now?
    >>>
    >>>
    >>>
    >>>
    >>> There haven't been any scheduler changes for some time. There have
    >>> been a
    >>> few low-level SMT changes I think.
    >>>
    >>> Are you able to identify which kernel version broke it?
    >>>
    >>
    >> Still have not narrowed this down too far, disabling SMT made no
    >> difference, disabling SMP did, which I was expecting.
    >>
    >> Steve
    >>
    >
    > I initially saw this with 2.6.12-rc1 and every version up through rc3. I
    > haven't tried with later versions. :-/ I initially reported here:
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=111235814529008&w=2
    >
    > The way that I got around it was to compile in my aic7xxx driver instead
    > of making it a module. I have also recently received an email from
    > someone saying that disabling module unloading would also solve it. That
    > very well may be true since I did run into another booting problem
    > (2.6.12-rc5) that disabling module unloading fixed :-/ I haven't had a
    > chance to go back and check this out though.
    >
    > So to summarize: I have a dual 933 with aic7xxx compiled in to get
    > passed the problem described above. I have a dual 2.6 w/HT that I have
    > disabled module unloading to get passed another boot condition.
    >
    >

    I found another system which exhibits the problem, a dual Xeon
    with HT support.

    Here is one of the cpus from /proc/cpuinfo

    processor : 0
    vendor_id : GenuineIntel
    cpu family : 15
    model : 1
    model name : Intel(R) Xeon(TM) CPU 1.40GHz
    stepping : 1
    cpu MHz : 1393.851
    cache size : 256 KB
    physical id : 0
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
    bogomips : 2752.51

    I discovered that if I disable P4 support on this host and run with
    P3 Xeon support instead, things start working. The host type in the
    boot up is identified as a P4/Xeon:

    Jun 14 11:25:19 k4 kernel: Booting processor 2/2 eip 3000
    Jun 14 11:25:19 k4 kernel: CPU 2 irqstacks, hard=c03e7000 soft=c03df000
    Jun 14 11:25:19 k4 kernel: Initializing CPU#2
    Jun 14 11:25:19 k4 kernel: CPU: Trace cache: 12K uops, L1 D cache: 8K
    Jun 14 11:25:19 k4 kernel: CPU: L2 cache: 256K
    Jun 14 11:25:19 k4 kernel: CPU: L3 cache: 512K
    Jun 14 11:25:19 k4 kernel: CPU: Physical Processor ID: 1
    Jun 14 11:25:19 k4 kernel: Intel machine check architecture supported.
    Jun 14 11:25:19 k4 kernel: Intel machine check reporting enabled on CPU#2.
    Jun 14 11:25:19 k4 kernel: CPU2: Intel P4/Xeon Extended MCE MSRs (12) available
    Jun 14 11:25:19 k4 kernel: CPU2: Intel(R) Xeon(TM) CPU 1.40GHz stepping 01

    So is this some P4 specific optimization which is not working as
    intended?

    Steve

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