DB2 FOR LUW / DB2FORLUW / 950 - DB2

This APAR describes a deadlatch situation with the deadlock 
event monitor (DB2EVMTI). 
 
1) DB2EVMTI is trying to log deadlock events to its target 
tables and finds that the tables are already locked. 
2) This lock situation triggers another deadlock and the 
deadlock event monitor while trying to generate the new deadlock 
event enters into a deadlatch situation with the deadlock 
detector (DB2DLOCK). 
 
The latch that is been waited on is 
SQLO_LT_SQM_EVMON_MGR__EM_LIST_LATCH. As the db2evmti is holding 
also SQLO_LT_sqeLocalDatabase__dblatch, new connections will be 
not possible and we will have the system hung. 
 
Stack for db2evmti 
 
00002B7C23CA4F7F ossDumpStackTraceEx + 0x01f7 
  00002B7C23CA0ABA _ZN11OSSTrapFile6dumpExEmiP7siginfoPvm + 
0x00b4 
  00002B7C23CA0B81 _ZN11OSSTrapFile4dumpEmiP7siginfoPv + 0x0009 
  00002B7C20216103 sqlo_trce + 0x03f3 
  00002B7C2025650F sqloDumpDiagInfoHandler + 0x00dd 
  000000364280EB10 __invoke_dynamic_linker__ + 0x1280 
  00000036420BAA27 __sched_yield + 0x0007 
  00002B7C1EFA5A3D sqloSpinLockConflict + 0x015d 
  00002B7C20DDC701 _Z12sqlxp_errmsgP8sqlxp_cbhhijP5Token + 
0x000b 
  00002B7C1F93E0BF 
_ZN13sqm_evmon_mgr17gen_en_dlock_connEP14sqeApplicationPPc + 
0x008b 
  00002B7C1F928030 
_ZN15sqm_dlconn_list17gen_dlconn_eventsEPK8sqeAgentP8SQLP_LRB + 
0x0812 
  00002B7C1F0086D2 
_Z8sqlplfndP8sqeAgentP14SQLP_LOCK_INFOP8SQLP_LCBP9SQLP_LHSHP15SQ 
LP_LTRN_CHAINP8SQLP_LRBSA_SA_P8SQLP_AWBbb 
+ 0x0a02 
  00002B7C20DF7491 _Z7sqlplrqP8sqeAgentP14SQLP_LOCK_INFO + 
0x1c71 
  00002B7C20DB5366 
_Z13sqldLockTableP8sqeAgentP14SQLP_LOCK_INFOjti + 0x00d2 
  00002B7C1ECB342A 
_Z24sqldGetTableCacheAndLockP8sqeAgentiitiiimiP14SQLP_LOCK_INFOP 
P16SQLD_TABLE_CACHE 
+ 0x01e4 
  00002B7C1EC9060E 
_Z13sqldRowInsertP8sqeAgenttthmiPP10SQLD_VALUEP13SQLD_TDATARECP8 
SQLZ_RID 
+ 0x031c 
  00002B7C1F0CB965 
_Z8sqlrinsrP8sqlrr_cbttitPP10SQLD_VALUEmP8SQLZ_RID + 0x0069 
  00002B7C1F93344F _ZN17sqm_evmon_ttarget10write_dataEPcjh + 
0x190d 
  00002B7C1F93AD2E 
_ZN14sqmEvmonBuffer10write_dataEP16sqm_evmon_target + 0x00e4 
  00002B7C1EDDD76F _ZN14sqmEvmonWriter11evmonWriterEv + 0x061b 
  00002B7C1ECD47C0 _Z26sqleIndCoordProcessRequestP8sqeAgent + 
0x00e8 
  00002B7C1ECE1F5F _ZN8sqeAgent6RunEDUEv + 0x04c9 
  00002B7C1F1E6BF1 _ZN9sqzEDUObj9EDUDriverEv + 0x006d 
  00002B7C1F1E6B81 _Z10sqlzRunEDUPcj + 0x0009 
  00002B7C1EFD0C9A sqloEDUEntry + 0x02ea 
  000000364280673D pthread_cond_wait@@GLIBC_2.3.2 + 0x020d 
  00000036420D3D1D clone + 0x006d 
 
Waiting on latch type: (SQLO_LT_sqm_evmon_mgr__em_list_latch) - 
Address: (0x20069dcd0), Line: 630, File: sqlmemgr.C 
 
Stack for db2dlock 
 
00002B7C23CA4F7F ossDumpStackTraceEx + 0x01f7 
00002B7C23CA0ABA _ZN11OSSTrapFile6dumpExEmiP7siginfoPvm + 0x00b4 
00002B7C23CA0B81 _ZN11OSSTrapFile4dumpEmiP7siginfoPv + 0x0009 
00002B7C20216103 sqlo_trce + 0x03f3 
00002B7C2025650F sqloDumpDiagInfoHandler + 0x00dd 
000000364280EB10 address: 0x000000364280EB10 ; dladdress: 
0x0000003642800000 ; offset in lib: 0x000000000000EB10 ; 
00000036420D517A semtimedop + 0x000a 
00002B7C1EF89EE5 sqloWaitEDUWaitPost + 0x01ad 
00002B7C1F93A59A _ZN17sqm_evmon_ostream10write_dataEPKcjb + 
0x01ce 
00002B7C1F9396C6 _ZN14sqmEvmonWriter10sendStreamEPPvbS0_ + 
0x054a 
00002B7C1F942FA6 
_ZN13sqm_evmon_mgr9sendEventEPPcP17sqm_evmon_id_list + 0x00c2 
00002B7C1F93DFDB _ZN13sqm_evmon_mgr13gen_dlock_evtEPPc + 0x00d1 
00002B7C20262F9C 
_Z29sqlplReportLocalDeadlockEventP8SQLP_LCBjjP9SQLP_LHSH + 
0x05ae 
00002B7C20261D66 
_Z17sqlpKillIfWaitingP9SQLP_DBCBP8SQLP_LCBjiiiPiP12sqm_dlock_idi 
jii 
+ 0x0918 
 
Holding Latch type: (SQLO_LT_sqm_evmon_mgr__em_list_latch) -

**************************************************************** 
* USERS AFFECTED:                                              * 
* ALL                                                          * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* This APAR will collect diagnostic info regarding thedeadlock * 
* participants in a similar scenario. In a deadlockscenario if * 
* one of the participants is the deadlock evenmonitor itself,  * 
* DB2 will rollback the thread withoutcollecting any           * 
* information in the event monitor tables, butthe db2diag.log  * 
* will have information about the event.The information that   * 
* is logged when an event monitor isinvolved as one of the     * 
* participants in a deadlock is:"The deadlock detector has     * 
* detected a deadlock with an EventMonitor agent as a          * 
* participantInformation about this event will not be sent to  * 
* the EventMonitor. Some details are provided below"These      * 
* messages are being logged at WARNING level indb2diag.log and * 
* will be followed by information on theholder and waiter of   * 
* the lock for deadlocks in which eventmonitor is found as one * 
* of the participants.                                         * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 Version 9.5 and Fix Pack 8                    * 
****************************************************************

DB2 Version 9.5 Fix Pack 8 for Linux, UNIX, and Windows
 DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
 DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows
 

Problem was first fixed in DB2 Version 9.5 and Fick Pack 8

not known / see Local fix

forerunner  : APAR is sysrouted TO one or more of the following: IC75260 
follow-up : 

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

16.02.2011
30.06.2011
30.06.2011

9.5.