A DB2 prefetcher (db2pfchr) thread may initiate a panic and
shutdown of the DB2 instance after detecting an abnormal latch
state. This problem is indicated by a db2diag.log message
dumped at the time of the panic showing the following:
(1) the message reports a "Attempting to unlock an invalid
latch" string, with a ZRC line referencing
"SQLO_LATCH_ERROR_EXPECTED_HELD"
(2) the message references the bmpExist latch in the identity
field of the diagnostic message
(3) the stack information dumped along with the diagnostic
message shows the sqldAssertObjExists function.
An example message will resemble the following:
2015-05-17-00.01.14.938249-240 XXXXX LEVEL: Severe (OS)
PID : 4915702 TID : 8560 PROC :
db2sysc 0
INSTANCE: xxxxxx NODE : 000 DB : xxx
HOSTNAME: xxxxxx
EDUID : 8560 EDUNAME: db2pfchr (PB1) 0
FUNCTION: DB2 UDB, SQO Latch Tracing,
SQLO_SLATCH_CAS64::releaseConflict, probe:330
MESSAGE :
ZRC=0x870F011E=-2029059810=SQLO_LATCH_ERROR_EXPECTED_HELD
"expected latch to be held."
CALLED : OS, -, unspecified_system_function
DATA #1 : String, 39 bytes
Attempting to unlock an invalid latch:
DATA #2 : File name, 16 bytes
sqloLatchCAS64.C
DATA #3 : Source file line number, 8 bytes
1027
DATA #4 : Codepath, 8 bytes
4
DATA #5 : String, 125 bytes
0x0000000000000000: {
held X: 0
reserved for X: 0
shared holders: 0
firstSharIndex: 0x0
firstExclIndex: 0x0
}
DATA #6 : LatchMode, PD_TYPE_LATCH_MODE, 8 bytes
0x0 (invalid mode)
DATA #7 : String, 396 bytes
{
state = 0x0000000000000000
= {
held X: 0
reserved for X: 0
shared holders: 0
firstSharIndex: 0x0
firstExclIndex: 0x0
}
starve X mode = false
xWaitCount = 0
requestCount = 0
identity = SQLD_TCB::bmpExist (298)
}
DATA #8 : Pointer, 8 bytes
0x0770001233803020
DATA #9 : Hexdump, 16 bytes
0x0770001233803020 : 0000 0000 0000 0000 812A 0000 0000 0000
.........*......
CALLSTCK: (Static functions may not be resolved correctly, as
they are resolved to the nearest symbol)
[0] 0x090000000B995CE4
dumpDiagInfoAndPanic__17SQLO_SLATCH_CAS64CFCPCcCUiCUlT3ClT3CiT1T
3T7 +
0x30C
[1] 0x090000000CB539B0 releaseConflict__17SQLO_SLATCH_CAS64Fv
+ 0x104
[2] 0x090000000D100174
sqldAssertObjExists__FP16sqeLocalDatabaseP16SQL
B_OBJECT_DESCP12SQLD_OBJ_ HDLPC9SQLP_LSN8Ul + 0x17C
[3] 0x090000000CBADDC8
sqlbPFPrefetcherEntryPoint__FP16sqbPrefetcherEdu + 0x328
[4] 0x090000000D103748 RunEDU__16sqbPrefetcherEduFv + 0x34
[5] 0x090000000CDFA764 EDUDriver__9sqzEDUObjFv + 0x3EC
[6] 0x090000000CDFA33C sqlzRunEDU__FPcUi + 0x10
[7] 0x090000000CE07404 sqloEDUEntry + 0x264
[8] 0x09000000004C3D30 _pthread_body + 0xF0
[9] 0xFFFFFFFFFFFFFFFC ?unknown + 0xFFFFFFFF |
