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    SubjectRe: Checkin 7404ad3b6d04efbd918e9e2e776bf560fbedf47d breaks boot on KVM
    On Tue, Oct 14, 2008 at 09:00:55AM -0700, H. Peter Anvin wrote:
    > James Bottomley wrote:
    >> Actually, it is surprising. That patch takes the default arithmetic for
    >> calculating the disk size out of sd and uses a routine to do it more
    >> efficiently in lib/string_helpers.c
    >> So there are two problems: Why does it panic on revert (could you post
    >> the oops) and what does kvm object to in string_get_size ... it's a
    >> fairly innocuous routine as I read it ... your symptoms sound like the
    >> for loop isn't terminating.
    >
    > Here is the oops. Note that it does get well past the hang point before it
    > crashes. It is 100% reproducible.
    >
    > (...)
    > BUG: spinlock bad magic on CPU#0, swapper/1
    > lock: c0b75418, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
    > Pid: 1, comm: swapper Not tainted 2.6.27 #17
    > Call Trace:
    > [<c0597388>] ? printk+0xf/0x17
    > [<c03ac8ae>] spin_bug+0x75/0x80
    > [<c03ac97c>] _raw_spin_lock+0x1e/0xe4
    > [<c0412a3f>] ? serial8250_startup+0x33e/0x4e5
    > [<c0599821>] _spin_lock_irq+0x32/0x3a
    > [<c0412a3f>] ? serial8250_startup+0x33e/0x4e5
    > [<c0412a3f>] serial8250_startup+0x33e/0x4e5
    > [<c040f5fb>] uart_startup+0x84/0x143
    > [<c0410309>] uart_open+0x14b/0x381
    > [<c05996ba>] ? _spin_unlock+0x27/0x3c
    > [<c03f483f>] ? check_tty_count+0x3b/0x8a
    > [<c03f70b9>] tty_open+0x263/0x366
    > [<c0271b2a>] chrdev_open+0x168/0x180
    > [<c026df19>] __dentry_open+0x146/0x234
    > [<c026e08e>] nameidata_to_filp+0x1f/0x33
    > [<c02719c2>] ? chrdev_open+0x0/0x180
    > [<c0278ed1>] do_filp_open+0x342/0x659
    > [<c023651c>] ? trace_hardirqs_off+0xb/0xd
    > [<c05996ba>] ? _spin_unlock+0x27/0x3c
    > [<c026dcff>] do_sys_open+0x42/0xb7
    > [<c026ddb6>] sys_open+0x1e/0x26
    > [<c0201216>] init_post+0x2a/0x13c
    > [<c0203d53>] ? kernel_thread_helper+0x7/0x10

    It's a different issue.
    See: http://lkml.org/lkml/2008/10/13/470 and http://lkml.org/lkml/2008/10/13/474

    Marcin


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