Bug #42429 Falcon crash in Table::checkUniqueRecordVersion
Submitted: 28 Jan 2009 16:35 Modified: 7 May 2009 16:58
Reporter: Kevin Lewis Email Updates:
Status: Closed Impact on me:
Category:MySQL Server: Falcon storage engine Severity:S3 (Non-critical)
Version:6.0.9 OS:Any
Assigned to: Kevin Lewis CPU Architecture:Any
Triage: Triaged: D1 (Critical)

[28 Jan 2009 16:35] Kevin Lewis
While testing with RQG I found the following crash;

 	Transaction::getRelativeState(record=0x07a3fba8, flags=1)  Line 802
	Table::checkUniqueRecordVersion(recordNumber=11059, index=0x0419cba0, transaction=0x042cb3c0, record=0x07a3f738, syncUnique=0x0749df5c)  Line 2625
 	Table::checkUniqueIndex(index=0x0419cba0, transaction=0x042cb3c0, record=0x07a3f738, sync=0x0749df5c)  Line 2510
 	Table::insertIndexes(transaction=0x042cb3c0, record=0x07a3f738)  Line 1268 
 	Table::insert(transaction=0x042cb3c0, stream=0x040e7190)  Line 3056
 	StorageDatabase::insert(connection=0x041f2ed0, table=0x040bf878, stream=0x040e7190)  Line 267
 	StorageTable::insert()  Line 109
 	StorageInterface::write_row(buff=0x02a2ad48)  Line 1159 
 	ha_write_row(buf=0x02a2ad48)  Line 5438
 	. . .

It crashed in the following call to getRelativeState();

   if (isDuplicate(index, record, dup))
      if (state == Active)
         syncPrior.unlock(); // release lock before wait
         syncUnique->unlock(); // release lock before wait

         // Wait for that transaction, then restart checkUniqueIndexes()

>>>      state = transaction->getRelativeState(dup, WAIT_IF_ACTIVE);  <<<

After syncPrior was unlocked, the record version 'dup' was scavenged, probably by a commit doing releaseSavepoint or something.  By the time the debugger had stopped all threads, the memory location for dup had been reused for a completely different record number.  But while dup was free, it crashed in getRelativeState() at this line;
>>>	if (!record->isVersion())   <<<

How to repeat:
I was running this RQG script;
perl runall.pl --rows=1000 --threads=4 --mask=1487 --queries=1000000 --duration=3000 --basedir=C:\Work\bzr\Chg-09\mysql-6.0-falcon-team --engine=Falcon --grammar=conf/combinations.yy --gendata=conf/combinations.zz --reporter=ErrorLog,Backtrace

Suggested fix:
Records on the prior record chain will not be deleted while the checkUniqueRecordVersion() thread has the lock on syncPrior, but if it is release, that thread should have a useCount added.
[28 Jan 2009 16:37] Kevin Lewis
Verified by catching it in debugger.
[28 Jan 2009 21:06] Kevin Lewis
See http://lists.mysql.com/commits/64375

2983 Kevin Lewis	2009-01-28
      Bug #42429-Falcon crash in Table::checkUniqueRecordVersion
      increment the useCount for dup so it does not go away 
      immediately releasing syncPrior.
[13 Feb 2009 7:24] Bugs System
Pushed into 6.0.10-alpha (revid:alik@sun.com-20090211182317-uagkyj01fk30p1f8) (version source revid:kevin.lewis@sun.com-20090128191944-s2smemptgdxn17bf) (merge vers: 6.0.10-alpha) (pib:6)
[7 May 2009 16:58] MC Brown
Internal/test fix. No changelog entry required.