|
Problem IT18919
|
Status: Closed |
READAHEAD PREFETCHING COULD FIX INDEX RESERVED PAGE AND CAUSED UNPREDICTABLE BEHAVIORS |
| product: |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 |
| Problem description: |
DB2 could be locating keys on a reserved page during readahead
prefetching. This could happen when the index is under tree
structure modification on its root node and a rollback has
happened, which could result in an abandoned page. Under this
scenario, db2 could be fixing a reserved page other than normal
index pages that stores index key records, and perform searching
mechanism on the reserved page. As a result, db2 could be
behaving unexpectedly, such as bringing db2 down, or even cause
memory corruption under extreme case.
The following are example stacktraces for the crash:
29 Signal #11 (SIGSEGV): si_addr is 0x0000000000000000,
si_code is 0x00000080 (SI_KERNEL:Send by kernel.)
...
77 0x00002B062D3E24DC sqloEDUCodeTrapHandler + 0x02ac
78 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
79 0x0000003B4660F500 address: 0x0000003B4660F500 ; dladdress:
0x0000003B46600000 ; offset in lib: 0x000000000...
80 (/lib64/libpthread.so.0)
81 0x0000000000427ADA __intel_ssse3_rep_memcpy + 0x206a
82 (db2sysc 0)
83 0x00002B062BB591F5 _Z8sqlickeyP9SQLD_IDEFP8SQLD_KEYS2_ +
0x0085
84 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
85 0x00002B062BB523D2
_Z26sqliDoReadaheadPrefetchingP7SQLI_CBP28SQLI_READAHEAD_PREFETC
H_INFO + 0x0472
86 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
87 0x00002B062BB50DD5
_Z21sqliReadaheadPrefetchP7SQLI_CBP14SQLI_PAGE_DESCP28SQLI_READA
HEAD_PREFETCH_INFO + 0x0...
88 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
89 0x00002B062BB844F5 address: 0x00002B062BB844F5 ; dladdress:
0x00002B0627243000 ; offset in lib: 0x000000000...
90 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
91 0x00002B062E450534 _Z8sqlifnxtP7SQLI_CBP11SQLI_SFGLOB +
0x0bb4
92 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
93 0x00002B062E44B764
_Z7sqlirdkP8sqeAgentP10SQLI_IXPCRP9SQLD_IXCBmP8SQLD_KEYP12SQLI_K
EYDATAP9sqli_scanPi + 0x...
94 (/db2/db2bsp/sqllib/lib64/libdb2e.so.1)
<StackTrace>
[0] 0x090000000BCD87D4 pdLog + 0x2D4
[1] 0x09000000109444F0 sqlifix__FP7SQLI_CBP14SQLI_PAGE_DESCUii
+ 0xE90
[2] 0x0900000013144C40
sqliCheckThisPageForEndMilestone__FP7SQLI_CBP28SQLI_READAHEAD_PR
EFETCH_INFOPP14SQLI_PAGE_DESCT3li + 0x5C0
[3] 0x0900000013148BB8
sqliGetNextReadaheadPrefetchStartPoint__FP7SQLI_CBP28SQLI_READAH
EAD_PREFETCH_INFOPP14SQLI_PAGE_DESCT3i + 0x358
[4] 0x0900000013149938
sqliDoReadaheadPrefetching__FP7SQLI_CBP28SQLI_READAHEAD_PREFETCH
_INFO + 0x558
[5] 0x090000001314C320
sqliReadaheadPrefetch__FP7SQLI_CBP14SQLI_PAGE_DESCP28SQLI_READAH
EAD_PREFETCH_INFO + 0xD80
[6] 0x09000000133ADD58
sqldSeqDetCheck__FUiUsP16SQLB_OBJECT_DESCP16SQLD_SEQDET_INFOT1P8
sqeAgentP7SQLI_CBT1 + 0x318
[7] 0x09000000133AE048
sqliSeqDetCheck__FUiP7SQLI_CBP16SQLD_SEQDET_INFOT1Us + 0x148
[8] 0x09000000133B34DC
sqliMoveToNextLeaf__FP7SQLI_CBP12SQLI_KEYDATAi + 0x93C
[9] 0x09000000133CFA2C sqlifnxt__FP7SQLI_CBP11SQLI_SFGLOB +
0xD4C
[10] 0x090000000C263DE0
sqlirdk__FP8sqeAgentP10SQLI_IXPCRP9SQLD_IXCBUlP8SQLD_KEYP12SQLI_
KEYDATAP9sqli_scanPi + 0x11E0
[11] 0x090000000EC52E60 sqldIndexFetch__FP8SQLD_CCBP8SQLZ_RID
+ 0x5E0
[12] 0x090000000EC5FC98
sqldRowFetch__FP8sqeAgentP8SQLD_CCBUlT3PP10SQLD_VALUEP8SQLZ_RIDT
3P12SQLD_ID_LISTP9SQLP_LSN8 + 0x1798
[13] 0x09000000137FEA64
sqlriFetchPerm__FP8sqlrr_cbP9sqlri_taol + 0x104
[14] 0x09000000137FEE28 sqlritaSimplePerm__FP8sqlrr_cb + 0x348
[15] 0x09000000138612CC
sqlriExecThread__FP8sqlrr_cbP12sqlri_opparm + 0x84C
[16] 0x090000001386901C sqlrihsjn__FP8sqlrr_cb + 0x6DC
[17] 0x090000000C485328
sqlriExecThread__FP8sqlrr_cbP12sqlri_opparm + 0x848
[18] 0x090000000C487EFC
sqlriSectInvoke__FP8sqlrr_cbP12sqlri_opparm + 0x121C
[19] 0x0900000017ED7CF0 sqlrr_dss_router__FP8sqlrr_cb + 0xC90
[20] 0x0900000017EDBE50
sqlrr_subagent_router__FP8sqeAgentP12SQLE_DB2RA_T + 0x1D50
[21] 0x090000000C069A7C
sqleSubRequestRouter__FP8sqeAgentPUiPUl + 0xE9C
[22] 0x090000000C0874AC sqleProcessSubRequest__FP8sqeAgent +
0x34C
[23] 0x090000000BFEE12C RunEDU__8sqeAgentFv + 0x38C
[24] 0x090000000BFAB7B8 EDUDriver__9sqzEDUObjFv + 0x238
[25] 0x090000000BFABB1C sqlzRunEDU__FPcUi + 0x3C
[26] 0x090000000BDE24F8 sqloEDUEntry + 0x778
[27] 0x09000000004F6D30 _pthread_body + 0xF0
[28] 0xFFFFFFFFFFFFFFFC ?unknown + 0xFFFFFFFF |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* ALL *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 10.5 Fix Pack 9. *
**************************************************************** |
| Local Fix: |
This problem can be avoided by disabling readahead prefetching.
db2set DB2_READAHEAD_PREFETCH=false
followed by db2stop/db2start to pick up this change |
| Solution |
First fixed in DB2 Version 10.5 Fix Pack 9. |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 20.01.2017
27.09.2017
27.09.2017 |
| Problem solved at the following versions (IBM BugInfos) |
9.0.
|
| Problem solved according to the fixlist(s) of the following version(s) |
