Lock order reversal in 5.2-CURRENT

Terrence Koeman root at mediamonks.net
Tue Aug 10 11:30:27 PDT 2004


In addition to my compiler not working, I've encountered another problem,
the system just hung and dropped to the debugger on the serial port.

There's nothing in the logfiles, the output on the serial console was:

lock order reversal
 1st 0xc0645aa0 sched lock (sched lock) @ /usr/src/sys/vm/vm_zeroidle.c:156
 2nd 0xc06748c0 sio (sio) @ /usr/src/sys/dev/sio/sio.c:3039
KDB: stack backtrace:
kdb_backtrace(c05fe96f,c06748c0,c0636660,c0636660,c060eede) at
witness_checkorder(c06748c0,9,c060eede,bdf,da7a) at witness_checkorder+0x6a6
_mtx_lock_spin_flags(c06748c0,0,c060eede,bdf,a) at _mtx_lock_spin_flags+0x8d
siocnputc(c0636840,6b,5,d4dd7bf0,6b) at siocnputc+0x7a
cnputc(6b,da7a,1,c15f39a0,c0611cff) at cnputc+0x6a
putchar(6b,d4dd7bf0,c064ab40,0,c0686634) at putchar+0x5c
kvprintf(c0611cfe,c04c9930,d4dd7bf0,a,d4dd7c10) at kvprintf+0x8d
printf(c0611cfe,c,d4dd7c30,c04b2c9e,c0645aa0) at printf+0x55
trap(18,c0640010,10,c15f39a0,d4dd7cfc) at trap+0xc2
calltrap() at calltrap+0x5
--- trap 0xc, eip = 0xc04b3ed2, esp = 0xd4dd7c90, ebp = 0xd4dd7ce0 ---
mi_switch(1,0,c060d2be,9c,dbba0) at mi_switch+0x102
vm_pagezero(0,d4dd7d48,c05f8b5a,32b,e209f103) at vm_pagezero+0xe9
fork_exit(c059b140,0,d4dd7d48) at fork_exit+0xc7
fork_trampoline() at fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xd4dd7d7c, ebp = 0 ---
KDB: enter: witness_checkorder
[thread 100051]
Stopped at      kdb_enter+0x30: leave

This LOR is not on http://sources.zabbadoz.net/freebsd/lor.html, so I'm
guessing this one locked up my system.

I have ruled out broken hardware by swapping raid arrays with an identical
working system earier because of my compiler problem (see my earlier mail on

My dmesg and kernel config file are attached.

Please advice.

Terrence Koeman
MediaMonks B.V. (www.mediamonks.com)
Please quote all replies in correspondence.    
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