Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000) - Debian

This is a discussion on Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000) - Debian ; I've now been running git. I started with git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6.25..y.git I did a git bisect and found that the commit that introduced the bug is commit 94aa6550e8668fab1997e2d57a48b22cf68090b2 Author: Thomas Gleixner Date: Tue May 13 12:31:00 2008 +0200 x86: distangle ...

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Thread: Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000)

  1. Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000)


    I've now been running git. I started with
    git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6.25..y.git

    I did a git bisect and found that the commit that introduced the bug is

    commit 94aa6550e8668fab1997e2d57a48b22cf68090b2
    Author: Thomas Gleixner
    Date: Tue May 13 12:31:00 2008 +0200

    x86: distangle user disabled TSC from unstable

    upstream commit: 9ccc906c97e34fd91dc6aaf5b69b52d824386910

    tsc_enabled is set to 0 from the command line switch "notsc" and from
    the mark_tsc_unstable code. Seperate those functionalities and replace
    tsc_enable with tsc_disable. This makes also the native_sched_clock()
    decision when to use TSC understandable.

    Preparatory patch to solve the sched_clock() issue on 32 bit.

    Signed-off-by: Thomas Gleixner
    Signed-off-by: Chris Wright

    This commit changes file arch/x86/kernel/tsc_32.c

    I tried booting with notsc but I still got "BUG: Int 6: CR2 00000000"

    After looking at the commitdiff, I guessed that native_sched_clock() getscalled before tsc_init().
    http://git.kernel.org/?p=linux/kerne...48b22cf68090b2

    Prior to the commit native_sched_clock() looked at unitialised tsc_enable which holds 0
    so didn't attempt to access a TSC. After the commit native_sched_clock() looks at
    unitialised tsc_disable which holds 0 so attempts to access a TSC leading to the BUG:

    Starting with a kernel tree from immediately after the faulty commit. I made the following
    change which stops the BUG occuring.

    *** arch/x86/kernel/tsc_32.c.000 2008-07-30 13:07:57.000000000 +0100
    --- arch/x86/kernel/tsc_32.c 2008-07-30 13:09:57.000000000 +0100
    *************** unsigned long long native_sched_clock(vo
    *** 121,127 ****
    * very important for it to be as fast as the platform
    * can achive it. )
    */
    ! if (unlikely(tsc_disabled))
    /* No locking but a rare wrong value is not a big deal: */
    return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

    --- 121,127 ----
    * very important for it to be as fast as the platform
    * can achive it. )
    */
    ! if (unlikely(tsc_disabled || !cpu_has_tsc))
    /* No locking but a rare wrong value is not a big deal: */
    return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

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  2. Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000)

    On Wed, Jul 30, 2008 at 12:49:38PM +0000, bruce robson wrote:
    >
    > I've now been running git. I started with
    > git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6.25.y.git
    >
    > I did a git bisect and found that the commit that introduced the bug is
    >
    > commit 94aa6550e8668fab1997e2d57a48b22cf68090b2
    > Author: Thomas Gleixner
    > Date: Tue May 13 12:31:00 2008 +0200
    >
    > x86: distangle user disabled TSC from unstable
    >
    > upstream commit: 9ccc906c97e34fd91dc6aaf5b69b52d824386910
    >
    > tsc_enabled is set to 0 from the command line switch "notsc" and from
    > the mark_tsc_unstable code. Seperate those functionalities and replace
    > tsc_enable with tsc_disable. This makes also the native_sched_clock()
    > decision when to use TSC understandable.
    >
    > Preparatory patch to solve the sched_clock() issue on 32 bit.
    >
    > Signed-off-by: Thomas Gleixner
    > Signed-off-by: Chris Wright
    >
    > This commit changes file arch/x86/kernel/tsc_32.c


    Great, thanks Bruce! Can you file a bug on bugzilla.kernel.org with
    this information and let us know the number so we can track it?

    --
    dann frazier




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  3. Bug#488022: linux-image-2.6.25-2-486: Does not boot on Vortex86SX (BUG: Int 6: CR2 00000000)

    On Thu, Sep 25, 2008 at 01:11:38PM -0600, dann frazier wrote:
    > On Wed, Jul 30, 2008 at 12:49:38PM +0000, bruce robson wrote:
    > >
    > > I've now been running git. I started with
    > > git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6.25.y.git
    > >
    > > I did a git bisect and found that the commit that introduced the bug is
    > >
    > > commit 94aa6550e8668fab1997e2d57a48b22cf68090b2
    > > Author: Thomas Gleixner
    > > Date: Tue May 13 12:31:00 2008 +0200
    > >
    > > x86: distangle user disabled TSC from unstable
    > >
    > > upstream commit: 9ccc906c97e34fd91dc6aaf5b69b52d824386910
    > >
    > > tsc_enabled is set to 0 from the command line switch "notsc" and from
    > > the mark_tsc_unstable code. Seperate those functionalities and replace
    > > tsc_enable with tsc_disable. This makes also the native_sched_clock()
    > > decision when to use TSC understandable.
    > >
    > > Preparatory patch to solve the sched_clock() issue on 32 bit.
    > >
    > > Signed-off-by: Thomas Gleixner
    > > Signed-off-by: Chris Wright
    > >
    > > This commit changes file arch/x86/kernel/tsc_32.c

    >
    > Great, thanks Bruce! Can you file a bug on bugzilla.kernel.org with
    > this information and let us know the number so we can track it?


    Bruce, did you pass this upstream or is the bug fixed in current Lenny
    or unstable kernel images?

    Cheers,
    Moritz



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