Re: [Xen-devel] new(?) big ugly crash

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Can you easily reproduce this? All the subsequent oopses are because
our panic() when the mmu updates fail ought to be a BUG() [BUG doesn't
try to sync disks; panic does] ---- it's nothing to do with XFS.

If you do a debug build of Xen then we may get useful info out as to
why the mmu_update is failing.

 -- Keir

> 
> fresh pull and build tonight.  doing "/etc/init.d/xend stop" caused a 
> lot of havoc starting with:
> 
> Kernel panic: Failed to execute MMU updates
> 
> from the dom0 kerne and then a ton of consecutive Oopses and the 
> machine immediately rebooted.  This is but the first of a series of 
> Oopses from xfslogd.  (Which probably tried to sync disks when it 
> Oopsed to save data, which caused another Oops, making XFS try to sync, 
> etc...)
> 
> I'm rebuilding the dom-0 kernel with more debugging options turned on 
> (which I thought I had done) so if this happens again, maybe I'll have 
> better data.
> 
> I notice that the Oops stack passes through some IDE writing routines, 
> and I'm wondering if the recent crash-fix might not mess up XFS's 
> pagebufs somewhere.  XFS has its own set of filesystem cache structure 
> type things (I wish I had a more accurate explanation...) that it 
> manages itself to keep in sync with filesystem data and what it's 
> buffered in memory.  Is it possible that the recent fixes might 
> interfere with/bypass this and cause corruption/desynchronization of 
> filesystem cache and XFS pagebufs?  I assume from the missing #include 
> when I first started playing with Xen not too long ago that none of the 
> developers are using XFS and so would not have ever looked at this data 
> path through XFS?
> 
> 
> ksymoops 2.4.9 on i686 2.4.26-xeno-xen0.  Options used
>       -V (default)
>       -k /proc/ksyms (default)
>       -l /proc/modules (default)
>       -o /lib/modules/2.4.26-xeno-xen0/ (default)
>       -m /boot/System.map-2.4.26-xen0 (specified)
> 
> invalid operand: 0000
> CPU:    0
> EIP:    0819:[<c0105d2c>]    Not tainted
> Using defaults from ksymoops -t elf32-i386 -a i386
> EFLAGS: 00211246
> eax: c11ec000   ebx: c1173080   ecx: 00000000   edx: fbff9000
> esi: c11ec000   edi: c1173088   ebp: c11eda80   esp: c11eda5c
> ds: 0821   es: 0821   ss: 0821
> Process xfslogd/0 (pid: 8, stackpage=c11ed000)<1>
> Stack: 00000000 c01e547f 00000082 00000000 00000000 00000000 c1173080 
> c11ec000
>         c1173088 c11eda8c c01ddee7 00000000 00000001 c11ec000 c1173088 
> c1173088
>         c1173080 c1176400 c27270f0 00000000 c01de0ec c1173080 c11edc70 
> 00000000
> Call Trace: [<c01e547f>] [<c01ddee7>] [<c01de0ec>] [<c01d720f>] 
> [<c01bae08>]
>     [<c01bf749>] [<c01bdf22>] [<c01be7c8>] [<c01af95f>] [<c01acc69>] 
> [<c01a5b4e>]
>     [<c01abeeb>] [<c01cc10f>] [<c01ccfb5>] [<c01f4088>] [<c022307d>] 
> [<c021af2f>]
>     [<c021b613>] [<c0220730>] [<c01cd676>] [<c012d441>] [<c0105dbe>] 
> [<c0205071>]
>     [<c01091c2>] [<c01092b5>] [<c012d4b8>] [<c012d5aa>] [<c012d6fa>] 
> [<c012d7af>]
>     [<c0108c2a>] [<c01e8256>] [<c01e24f6>] [<c0108348>] [<c0105c01>] 
> [<c01d68f8>]
>     [<c01d69b3>] [<c01dd6ee>] [<c01d6980>]
> Warning (Oops_read): Code line not seen, dumping what data is available
> 
> 
>  >>EIP; c0105d2c <schedule+37c/390>   <=====
> 
>  >>eax; c11ec000 <_end+e7315c/41031bc>
>  >>ebx; c1173080 <_end+dfa1dc/41031bc>
>  >>esi; c11ec000 <_end+e7315c/41031bc>
>  >>edi; c1173088 <_end+dfa1e4/41031bc>
>  >>ebp; c11eda80 <_end+e74bdc/41031bc>
>  >>esp; c11eda5c <_end+e74bb8/41031bc>
> 
> Trace; c01e547f <evtchn_do_upcall+af/110>
> Trace; c01ddee7 <__down+77/f0>
> Trace; c01de0ec <__down_failed+8/c>
> Trace; c01d720f <.text.lock.xfs_buf+23/54>
> Trace; c01bae08 <xfs_getsb+48/50>
> Trace; c01bf749 <xfs_trans_getsb+39/b0>
> Trace; c01bdf22 <xfs_trans_apply_sb_deltas+22/4b0>
> Trace; c01be7c8 <xfs_trans_commit+298/370>
> Trace; c01af95f <xfs_log_reserve+bf/d0>
> Trace; c01acc69 <xfs_iomap_write_allocate+2f9/4d0>
> Trace; c01a5b4e <xfs_iunlock+3e/80>
> Trace; c01abeeb <xfs_iomap+3db/540>
> Trace; c01cc10f <xfs_map_blocks+5f/e0>
> Trace; c01ccfb5 <xfs_page_state_convert+435/5c0>
> Trace; c01f4088 <add_timer_randomness+d8/f0>
> Trace; c022307d <idedisk_end_request+bd/f0>
> Trace; c021af2f <ide_do_request+3f/1d0>
> Trace; c021b613 <ide_intr+133/1b0>
> Trace; c0220730 <ide_dma_intr+0/c0>
> Trace; c01cd676 <linvfs_writepage+86/130>
> Trace; c012d441 <write_some_buffers+c1/120>
> Trace; c0105dbe <__wake_up+7e/90>
> Trace; c0205071 <serial_console_write+121/220>
> Trace; c01091c2 <__call_console_drivers+62/70>
> Trace; c01092b5 <call_console_drivers+65/120>
> Trace; c012d4b8 <write_unlocked_buffers+18/20>
> Trace; c012d5aa <sync_buffers+1a/70>
> Trace; c012d6fa <fsync_dev+1a/50>
> Trace; c012d7af <sys_sync+f/20>
> Trace; c0108c2a <panic+11a/130>
> Trace; c01e8256 <_flush_page_update_queue+76/80>
> Trace; c01e24f6 <destroy_context+166/170>
> Trace; c0108348 <__mmdrop+28/50>
> Trace; c0105c01 <schedule+251/390>
> Trace; c01d68f8 <pagebuf_iodone_daemon+108/170>
> Trace; c01d69b3 <pagebuf_logiodone_daemon+33/40>
> Trace; c01dd6ee <arch_kernel_thread+2e/40>
> Trace; c01d6980 <pagebuf_logiodone_daemon+0/40>
> 
> 
> 
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