Re: [BUG] 2.6.20-rc3-mm1: can not mount root

[Andrew Morton]

On Fri, 5 Jan 2007 17:20:38 +0300
"Tomasz Kvarsin" <kvarsin@xxxxxxxxx> wrote:

> I can not boot machine with 2.6.20-rc3-mm1 and  2.6.20-rc2-mm1.
> I made binary search, patch bellow cause this bug:
> $quilt top
> patches/sched-improve-sched_clock-on-i686.patch
> 
> backtrace which I got by connecting "gdb" to machine:

How did you manage to use gdb on an i386 kernel?  Using qemu or something?

> _raw_spin_lock (lock=0xc06c0c60) at lib/spinlock_debug.c:108
> 108                     for (i = 0; i < loops; i++) {
> (gdb) bt
> #0  _raw_spin_lock (lock=0xc06c0c60) at lib/spinlock_debug.c:108
> #1  0xc056ac42 in _spin_lock (lock=0xc06c0c60) at kernel/spinlock.c:182
> #2  0xc011c3bb in vprintk (fmt=0xc0649c00 "<0>BUG: spinlock %s on
> CPU#%d, %s/%d\n",
>     args=0xc1167a84 "") at kernel/printk.c:534
> #3  0xc011c6c7 in printk (fmt=0xc0649c00 "<0>BUG: spinlock %s on
> CPU#%d, %s/%d\n")
>     at kernel/printk.c:508
> #4  0xc027be42 in spin_bug (lock=0xc06c0c60, msg=0xc065fc00
> "recursion") at lib/spinlock_debug.c:61
> #5  0xc027c178 in _raw_spin_lock (lock=0xc06c0c60) at lib/spinlock_debug.c:79
> #6  0xc056ac42 in _spin_lock (lock=0xc06c0c60) at kernel/spinlock.c:182
> #7  0xc011c3bb in vprintk (fmt=0xc0626ed0 "<1>BUG: unable to handle
> kernel paging request",
>     args=0xc1167b8c "") at kernel/printk.c:534
> #8  0xc011c6c7 in printk (fmt=0xc0626ed0 "<1>BUG: unable to handle
> kernel paging request")
>     at kernel/printk.c:508
> #9  0xc0116de4 in do_page_fault (regs=0xc1167bcc, error_code=0) at
> arch/i386/mm/fault.c:555
> #10 0xc056b11c in page_fault ()
> #11 0xc0808160 in ?? ()
> #12 0xc0626ed0 in kallsyms_token_index ()
> #13 0xc1167cac in ?? ()
> #14 0x00000001 in ?? ()
> #15 0xc0808163 in printk_buf.19225 ()
> #16 0xc1167c0c in ?? ()
> #17 0x00000000 in ?? ()

It looks like the machine was trying to oops, only it gets stuck on
logbuf_lock.  Perhaps it hit an oops while running printk_clock() inside
vprintk() then tried to go recursive.

oopses while holding logbuf_lock are rare, and appear to be fatal.  Perhaps
we should ignore logbuf_lock if oops_in_progress, but the chances are we'll
just hit the same oops again..

Do you have "time" on the kernel boot command line?  If so, does removing
that option make the hang go away?  
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