Fix off-by-one bug in LWLockRegisterTranche().

tglsfdc · tglsfdc · commit 4bfc5f1396b1 · 2014-04-25T15:59:57.000-04:00
Original coding failed to enlarge the array as required if
the requested tranche_id was equal to LWLockTranchesAllocated.

In passing, fix poor style of not casting the result of (re)palloc.
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
@@ -350,8 +350,9 @@ CreateLWLocks(void)
 	if (LWLockTrancheArray == NULL)
 	{
 		LWLockTranchesAllocated = 16;
-		LWLockTrancheArray = MemoryContextAlloc(TopMemoryContext,
-			LWLockTranchesAllocated * sizeof(LWLockTranche *));
+		LWLockTrancheArray = (LWLockTranche **)
+			MemoryContextAlloc(TopMemoryContext,
+							   LWLockTranchesAllocated * sizeof(LWLockTranche *));
 	}
 
 	MainLWLockTranche.name = "main";
@@ -423,11 +424,12 @@ LWLockRegisterTranche(int tranche_id, LWLockTranche *tranche)
 	{
 		int		i = LWLockTranchesAllocated;
 
-		while (i < tranche_id)
+		while (i <= tranche_id)
 			i *= 2;
 
-		LWLockTrancheArray = repalloc(LWLockTrancheArray,
-									  i * sizeof(LWLockTranche *));
+		LWLockTrancheArray = (LWLockTranche **)
+			repalloc(LWLockTrancheArray,
+					 i * sizeof(LWLockTranche *));
 		LWLockTranchesAllocated = i;
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -350,8 +350,9 @@ CreateLWLocks(void)`
`350`	`350`	`if (LWLockTrancheArray == NULL)`
`351`	`351`	`{`
`352`	`352`	`LWLockTranchesAllocated = 16;`
`353`		`- LWLockTrancheArray = MemoryContextAlloc(TopMemoryContext,`
`354`		`- LWLockTranchesAllocated * sizeof(LWLockTranche *));`
	`353`	`+ LWLockTrancheArray = (LWLockTranche **)`
	`354`	`+ MemoryContextAlloc(TopMemoryContext,`
	`355`	`+ LWLockTranchesAllocated * sizeof(LWLockTranche *));`
`355`	`356`	`}`
`356`	`357`
`357`	`358`	`MainLWLockTranche.name = "main";`
`@@ -423,11 +424,12 @@ LWLockRegisterTranche(int tranche_id, LWLockTranche *tranche)`
`423`	`424`	`{`
`424`	`425`	`int i = LWLockTranchesAllocated;`
`425`	`426`
`426`		`- while (i < tranche_id)`
	`427`	`+ while (i <= tranche_id)`
`427`	`428`	`i *= 2;`
`428`	`429`
`429`		`- LWLockTrancheArray = repalloc(LWLockTrancheArray,`
`430`		`- i * sizeof(LWLockTranche *));`
	`430`	`+ LWLockTrancheArray = (LWLockTranche **)`
	`431`	`+ repalloc(LWLockTrancheArray,`
	`432`	`+ i * sizeof(LWLockTranche *));`
`431`	`433`	`LWLockTranchesAllocated = i;`
`432`	`434`	`}`
`433`	`435`