DB2 FOR LUW / DB2FORLUW / B10 - DB2

The issue is a race condition caused by a lack of memory
barriers when barrierWaitInterruptible() is used.  The unused
function barrierWait() may also have a similar issue, and that
will be fixed as well.

The hang includes the following stacks:

================================================================
================
=== 35184.248967.014.stack.txt:                          248967
- db2agntcol (BLUDB) 14 [-]
0x000010001664FF80 ossWasteTime + 0x0050
0x0000100009A12B68
ibm_cde::query::NativeSortCB::paradisSort(ibm_cde::query::NSJob*
, unsigned long) + 0x0f38
0x0000100009A1135C ibm_cde::query::NativeSortCB::sort(unsigned
int) + 0x0d0c
0x000010000996479C
ibm_cde::query::SortEvaluator::sortPartition(ibm_cde::query::Sor
tPartition*) + 0x014c
0x00001000099628B0
ibm_cde::query::SortEvaluator::processInputsSynchronously() +
0x0590
0x0000100006CA685C ibm_cde::query::Evaluator::evaluate(bool,
bool, ibm_cde::query::Evaluator::EvaluatorRestartState&,
ibm_cde::query::OptPredicateTracker*) + 0x088c
0x0000100006BA279C
ibm_cde::query::EvaluationRoutine::evaluate(unsigned int,
sql_static_data*) + 0x03ac
0x0000100007AC3E88
ibm_cde::query::Scheduler::evaluateChain(ibm_cde::query::Evaluat
ionRoutine*, unsigned long&, unsigned int) + 0x0418
0x0000100007AC0F18
ibm_cde::query::Scheduler::runWorkerThread(void*, int*) + 0x03b8
0x0000100007AC8CDC ibm_cde::query::cdeEntryPointImpl(sqeAgent*,
void*, void*) + 0x00bc
0x0000100008CFBFDC cdeInterface::startCdeSubagent(sqeAgent*) +
0x00ec
0x000010000F214384 sqlriInvokeCde(sqlrr_cb*) + 0x0064
0x000010000F0487F0 sqlriSectInvoke(sqlrr_cb*, sqlri_opparm*) +
0x0410


================================================================
================
=== 35184.226015.014.stack.txt:                          226015
- db2agntcol (BLUDB) 14 [-]
=== 35184.226037.014.stack.txt:                          226037
- db2agntcol (BLUDB) 14 [-]
=== 35184.248731.014.stack.txt:                          248731
- db2agntcol (BLUDB) 14 [-]
=== 35184.249369.014.stack.txt:                          249369
- db2agntcol (BLUDB) 14 [-]
0x00001000000942B8 __nanosleep + 0x0088
0x0000100009A107EC ibm_cde::query::NativeSortCB::sort(unsigned
int) + 0x019c
0x000010000996479C
ibm_cde::query::SortEvaluator::sortPartition(ibm_cde::query::Sor
tPartition*) + 0x014c
0x00001000099628B0
ibm_cde::query::SortEvaluator::processInputsSynchronously() +
0x0590
0x0000100006CA685C ibm_cde::query::Evaluator::evaluate(bool,
bool, ibm_cde::query::Evaluator::EvaluatorRestartState&,
ibm_cde::query::OptPredicateTracker*) + 0x088c
0x0000100006BA279C
ibm_cde::query::EvaluationRoutine::evaluate(unsigned int,
sql_static_data*) + 0x03ac
0x0000100007AC3E88
ibm_cde::query::Scheduler::evaluateChain(ibm_cde::query::Evaluat
ionRoutine*, unsigned long&, unsigned int) + 0x0418
0x0000100007AC0F18
ibm_cde::query::Scheduler::runWorkerThread(void*, int*) + 0x03b8
0x0000100007AC8CDC ibm_cde::query::cdeEntryPointImpl(sqeAgent*,
void*, void*) + 0x00bc
0x0000100008CFBFDC cdeInterface::startCdeSubagent(sqeAgent*) +
0x00ec
0x000010000F214384 sqlriInvokeCde(sqlrr_cb*) + 0x0064
0x000010000F0487F0 sqlriSectInvoke(sqlrr_cb*, sqlri_opparm*) +
0x0410

This is on power pc which is heavily inlined.
There may be some barrier related functions on the stack between
paradisSort and ossWasteTime on other platforms.

****************************************************************
* USERS AFFECTED:                                              *
* All                                                          *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* None                                                         *
****************************************************************

There are 2 possible workarounds:

1)Re-submitting the query, with a different system workload may
works.

2)The using of the following Registry setting :

db2set DB2_REDUCED_OPTIMIZATION=COL_NO_OLAP

or passing it to the query in  embedded guidelines :

/* 



*/

not known / see Local fix

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

25.06.2020
28.01.2021
28.01.2021