Occasional wedging entering DDB via serial break
Robert Watson
rwatson at FreeBSD.org
Sun Dec 26 14:40:48 PST 2004
I'm seeing occasional wedging attempting to enter DDB via a serial break
on a dual-Xeon box (4 logical processors). The symptoms usually look
something like this:
hippy# ./tmp.csh
~KDB: enter: Line break on console
[thread pid 560 tid 100202 ]
Stopped at kdb_enter+0x2c: leave
db> show alllocks
db> cont
load: 0.04 cmd: super-smack 619 [runnable] 0.02u 0.51s 2% 2216k
~KDB: enter: Line break on console
[thread pid 560 tid 100201 ]
Stopped at kdb_enter+0x2c: leave
db> show alllocks
Process 560 (mysqld)
Thread 0x18769
exclusive sleep mutex so_rcv r = 0 (0xc2a25bcc) locked @
kern/uipc_usrreq.c:464
exclusive sleep mutex unp r = 0 (0xc091a740) locked @
kern/uipc_usrreq.c:392
db> cont
load: 0.92 cmd: super-smack 619 [runnable] 0.05u 1.36s 6% 2216k
~KDB: enter: Line break on console
[thread pid 560 tid 100199 ]
Stopped at kdb_enter+0x2c: leave
db> show alllocks
db> cont
load: 2.12 cmd: super-smack 616 [running] 0.08u 2.90s 10% 2216k
~KDB: enter: Line break on console
<wedge>
After that point, a serial break will no longer drop to DDB, respond to
pings, etc. The box is running 6.x-CURRENT from this morning. Is anyone
else seeing this, or does anyone else have ideas about what might cause
this?
Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org Principal Research Scientist, McAfee Research
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