bk commit into 6.0 tree (cpowers:1.2637) BUG#35692

[cpowers]

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ChangeSet@stripped, 2008-04-10 00:32:33-05:00, cpowers@stripped +2 -0
  Bug#35692, "Running falcon_record_cache_memory_leak2-big crashes Falcon"
  
  Removed deadlock. Table::rollbackRecord() locked syncPrior(Shared) before
  calling Table::insert(), but Table::insert() locks Table::syncObject. The
  Table lock must always be taken before the prior record version lock. 
  
  Now Table::rollbackRecord() holds syncPrior(Shared) just long enough to
  get the prior record and addRef, and unlocks syncPrior before calling ::insert().
  
  RecordVersion::scavenge(): Loop through prior versions with shared lock. Change
  prior version linkage under exclusive lock.

  storage/falcon/RecordVersion.cpp@stripped, 2008-04-10 00:32:31-05:00, cpowers@stripped
+5 -1
    Use syncPrior(Shared) to find prior version. Use exclusive to setPriorVersion().

  storage/falcon/Table.cpp@stripped, 2008-04-10 00:32:31-05:00, cpowers@stripped +19 -9
    Table::rollbackRecord: Hold syncPrior(Shared) long enough to get the prior
    version and addref. Unlock before calling insert.

diff -Nrup a/storage/falcon/RecordVersion.cpp b/storage/falcon/RecordVersion.cpp
--- a/storage/falcon/RecordVersion.cpp	2008-04-09 09:51:53 -05:00
+++ b/storage/falcon/RecordVersion.cpp	2008-04-10 00:32:31 -05:00
@@ -239,7 +239,7 @@ void RecordVersion::scavenge(TransId tar
 		return;
 
 	Sync syncPrior(getSyncPrior(), "RecordVersion::scavenge(2)");
-	syncPrior.lock(Exclusive);
+	syncPrior.lock(Shared);
 	
 	Record *rec = priorVersion;
 	Record *ptr = NULL;
@@ -268,6 +268,10 @@ void RecordVersion::scavenge(TransId tar
 	
 	Record *prior = priorVersion;
 	prior->addRef();
+
+	syncPrior.unlock();
+	syncPrior.lock(Exclusive);
+	
 	setPriorVersion(rec);
 	//ptr->setPriorVersion(NULL);
 	ptr->state = recEndChain;
diff -Nrup a/storage/falcon/Table.cpp b/storage/falcon/Table.cpp
--- a/storage/falcon/Table.cpp	2008-04-09 15:48:57 -05:00
+++ b/storage/falcon/Table.cpp	2008-04-10 00:32:31 -05:00
@@ -963,12 +963,6 @@ Record* Table::backlogFetch(int32 record
 
 Record* Table::rollbackRecord(RecordVersion * recordToRollback, Transaction *transaction)
 {
-	Sync syncPrior(getSyncPrior(recordToRollback), "Table::rollbackRecord");
-	
-	//cwp tbd: Problem if systemConnection->rollback() and table deleted
-	if (!transaction->systemTransaction)
-		syncPrior.lock(Shared);
-
 #ifdef CHECK_RECORD_ACTIVITY
 	recordToRollback->active = false;
 #endif
@@ -976,12 +970,25 @@ Record* Table::rollbackRecord(RecordVers
 	int priorState = recordToRollback->state;
 	recordToRollback->state = recRollback;
 
-	// Find the record that will become the current version.
+	// Hold syncPrior long enough to get prior version and addRef. Unlock before insert().
+	
+	Sync syncPrior(getSyncPrior(recordToRollback), "Table::rollbackRecord");
+
+	if (!transaction->systemTransaction)
+		syncPrior.lock(Shared);
 
+	// Find the record that will become the current version.
+	
 	Record *priorRecord = recordToRollback->getPriorVersion();
 
 	if (priorRecord)
+		{
+		priorRecord->addRef();
 		priorRecord->setSuperceded(false);
+		}
+	
+	if (!transaction->systemTransaction)
+		syncPrior.unlock();
 
 	// Replace the current version of this record.
 
@@ -1002,6 +1009,9 @@ Record* Table::rollbackRecord(RecordVers
 
 	if (backloggedRecords)
 		deleteRecordBacklog(recordToRollback->recordNumber);
+	
+	if (priorRecord)
+		priorRecord->release();
 			
 	return priorRecord;
 }
@@ -3262,8 +3272,8 @@ void Table::validateAndInsert(Transactio
 		if (prior)
 			{
 			syncTable.lock(Exclusive);
-			syncPrior.lock(Shared);
 			Record *current = fetch(record->recordNumber);
+			syncPrior.lock(Shared);
 
 			if (current)
 				{
@@ -3282,8 +3292,8 @@ void Table::validateAndInsert(Transactio
 
 					if (transaction->waitForTransaction(transId))
 						{
-						syncPrior.lock(Shared);
 						current = fetch(record->recordNumber);
+						syncPrior.lock(Shared);
 						
 						if (current == prior)
 							current->release();