4 files changed, 26 insertions, 34 deletions

diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index 1efe0201a79..cc3af2d6156 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -163,15 +163,32 @@ InitShmemAllocation(void)
 /*
  * ShmemAlloc -- allocate max-aligned chunk from shared memory
  *
- * Assumes ShmemLock and ShmemSegHdr are initialized.
+ * Throws error if request cannot be satisfied.
  *
- * Returns: real pointer to memory or NULL if we are out
- *		of space.  Has to return a real pointer in order
- *		to be compatible with malloc().
+ * Assumes ShmemLock and ShmemSegHdr are initialized.
  */
 void *
 ShmemAlloc(Size size)
 {
+	void	   *newSpace;
+
+	newSpace = ShmemAllocNoError(size);
+	if (!newSpace)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of shared memory (%zu bytes requested)",
+						size)));
+	return newSpace;
+}
+
+/*
+ * ShmemAllocNoError -- allocate max-aligned chunk from shared memory
+ *
+ * As ShmemAlloc, but returns NULL if out of space, rather than erroring.
+ */
+void *
+ShmemAllocNoError(Size size)
+{
 	Size		newStart;
 	Size		newFree;
 	void	   *newSpace;
@@ -206,11 +223,7 @@ ShmemAlloc(Size size)
 
 	SpinLockRelease(ShmemLock);
 
-	if (!newSpace)
-		ereport(WARNING,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
-
+	/* note this assert is okay with newSpace == NULL */
 	Assert(newSpace == (void *) CACHELINEALIGN(newSpace));
 
 	return newSpace;
@@ -293,7 +306,7 @@ ShmemInitHash(const char *name, /* table string name for shmem index */
 	 * The shared memory allocator must be specified too.
 	 */
 	infoP->dsize = infoP->max_dsize = hash_select_dirsize(max_size);
-	infoP->alloc = ShmemAlloc;
+	infoP->alloc = ShmemAllocNoError;
 	hash_flags |= HASH_SHARED_MEM | HASH_ALLOC | HASH_DIRSIZE;
 
 	/* look it up in the shmem index */
@@ -364,12 +377,6 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 			 */
 			Assert(shmemseghdr->index == NULL);
 			structPtr = ShmemAlloc(size);
-			if (structPtr == NULL)
-				ereport(ERROR,
-						(errcode(ERRCODE_OUT_OF_MEMORY),
-						 errmsg("not enough shared memory for data structure"
-								" \"%s\" (%zu bytes requested)",
-								name, size)));
 			shmemseghdr->index = structPtr;
 			*foundPtr = FALSE;
 		}
@@ -410,7 +417,7 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 	else
 	{
 		/* It isn't in the table yet. allocate and initialize it */
-		structPtr = ShmemAlloc(size);
+		structPtr = ShmemAllocNoError(size);
 		if (structPtr == NULL)
 		{
 			/* out of memory; remove the failed ShmemIndex entry */
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index 7cdb35541bf..4064b2033cc 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -1184,12 +1184,6 @@ InitPredicateLocks(void)
 		requestSize = mul_size((Size) max_table_size,
 							   PredXactListElementDataSize);
 		PredXact->element = ShmemAlloc(requestSize);
-		if (PredXact->element == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-			 errmsg("not enough shared memory for elements of data structure"
-					" \"%s\" (%zu bytes requested)",
-					"PredXactList", requestSize)));
 		/* Add all elements to available list, clean. */
 		memset(PredXact->element, 0, requestSize);
 		for (i = 0; i < max_table_size; i++)
@@ -1255,12 +1249,6 @@ InitPredicateLocks(void)
 		requestSize = mul_size((Size) max_table_size,
 							   RWConflictDataSize);
 		RWConflictPool->element = ShmemAlloc(requestSize);
-		if (RWConflictPool->element == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-			 errmsg("not enough shared memory for elements of data structure"
-					" \"%s\" (%zu bytes requested)",
-					"RWConflictPool", requestSize)));
 		/* Add all elements to available list, clean. */
 		memset(RWConflictPool->element, 0, requestSize);
 		for (i = 0; i < max_table_size; i++)
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 9a758bd9160..33e7023656a 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -194,14 +194,10 @@ InitProcGlobal(void)
 	 * between groups.
 	 */
 	procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
+	MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
 	ProcGlobal->allProcs = procs;
 	/* XXX allProcCount isn't really all of them; it excludes prepared xacts */
 	ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
-	if (!procs)
-		ereport(FATAL,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
-	MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
 
 	/*
 	 * Also allocate a separate array of PGXACT structures.  This is separate
diff --git a/src/include/storage/shmem.h b/src/include/storage/shmem.h
index 6468e6627ab..2560e6c6da5 100644
--- a/src/include/storage/shmem.h
+++ b/src/include/storage/shmem.h
@@ -35,6 +35,7 @@ typedef struct SHM_QUEUE
 extern void InitShmemAccess(void *seghdr);
 extern void InitShmemAllocation(void);
 extern void *ShmemAlloc(Size size);
+extern void *ShmemAllocNoError(Size size);
 extern bool ShmemAddrIsValid(const void *addr);
 extern void InitShmemIndex(void);
 extern HTAB *ShmemInitHash(const char *name, long init_size, long max_size,