postgresql-syntax-0.1: foreign/libpg_query/src/postgres/src_backend_utils_mmgr_mcxt.c
/*--------------------------------------------------------------------
* Symbols referenced in this file:
* - ErrorContext
* - MemoryContextReset
* - MemoryContextDeleteChildren
* - MemoryContextDelete
* - MemoryContextSetParent
* - pfree
* - MemoryContextCallResetCallbacks
* - MemoryContextResetOnly
* - repalloc
* - MemoryContextStats
* - MemoryContextStatsInternal
* - TopMemoryContext
* - pstrdup
* - MemoryContextStrdup
* - MemoryContextAlloc
* - CurrentMemoryContext
* - palloc
* - MemoryContextAllocZeroAligned
* - MemoryContextAllocZero
* - palloc0
* - MemoryContextCreate
* - MemoryContextInit
* - MemoryContextAllowInCriticalSection
* - CurrentMemoryContext
* - MemoryContextDelete
* - palloc0
*--------------------------------------------------------------------
*/
/*-------------------------------------------------------------------------
*
* mcxt.c
* POSTGRES memory context management code.
*
* This module handles context management operations that are independent
* of the particular kind of context being operated on. It calls
* context-type-specific operations via the function pointers in a
* context's MemoryContextMethods struct.
*
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/utils/mmgr/mcxt.c
*
*-------------------------------------------------------------------------
*/
/* see palloc.h. Must be before postgres.h */
#define MCXT_INCLUDE_DEFINITIONS
#include "postgres.h"
#include "miscadmin.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
/*****************************************************************************
* GLOBAL MEMORY *
*****************************************************************************/
/*
* CurrentMemoryContext
* Default memory context for allocations.
*/
__thread MemoryContext CurrentMemoryContext = NULL;
/*
* Standard top-level contexts. For a description of the purpose of each
* of these contexts, refer to src/backend/utils/mmgr/README
*/
__thread MemoryContext TopMemoryContext = NULL;
__thread MemoryContext ErrorContext = NULL;
/* This is a transient link to the active portal's memory context: */
static void MemoryContextCallResetCallbacks(MemoryContext context);
static void MemoryContextStatsInternal(MemoryContext context, int level);
/*
* You should not do memory allocations within a critical section, because
* an out-of-memory error will be escalated to a PANIC. To enforce that
* rule, the allocation functions Assert that.
*/
#define AssertNotInCriticalSection(context) \
Assert(CritSectionCount == 0 || (context)->allowInCritSection)
/*****************************************************************************
* EXPORTED ROUTINES *
*****************************************************************************/
/*
* MemoryContextInit
* Start up the memory-context subsystem.
*
* This must be called before creating contexts or allocating memory in
* contexts. TopMemoryContext and ErrorContext are initialized here;
* other contexts must be created afterwards.
*
* In normal multi-backend operation, this is called once during
* postmaster startup, and not at all by individual backend startup
* (since the backends inherit an already-initialized context subsystem
* by virtue of being forked off the postmaster). But in an EXEC_BACKEND
* build, each process must do this for itself.
*
* In a standalone backend this must be called during backend startup.
*/
void
MemoryContextInit(void)
{
AssertState(TopMemoryContext == NULL);
/*
* Initialize TopMemoryContext as an AllocSetContext with slow growth rate
* --- we don't really expect much to be allocated in it.
*
* (There is special-case code in MemoryContextCreate() for this call.)
*/
TopMemoryContext = AllocSetContextCreate((MemoryContext) NULL,
"TopMemoryContext",
0,
8 * 1024,
8 * 1024);
/*
* Not having any other place to point CurrentMemoryContext, make it point
* to TopMemoryContext. Caller should change this soon!
*/
CurrentMemoryContext = TopMemoryContext;
/*
* Initialize ErrorContext as an AllocSetContext with slow growth rate ---
* we don't really expect much to be allocated in it. More to the point,
* require it to contain at least 8K at all times. This is the only case
* where retained memory in a context is *essential* --- we want to be
* sure ErrorContext still has some memory even if we've run out
* elsewhere! Also, allow allocations in ErrorContext within a critical
* section. Otherwise a PANIC will cause an assertion failure in the error
* reporting code, before printing out the real cause of the failure.
*
* This should be the last step in this function, as elog.c assumes memory
* management works once ErrorContext is non-null.
*/
ErrorContext = AllocSetContextCreate(TopMemoryContext,
"ErrorContext",
8 * 1024,
8 * 1024,
8 * 1024);
MemoryContextAllowInCriticalSection(ErrorContext, true);
}
/*
* MemoryContextReset
* Release all space allocated within a context and delete all its
* descendant contexts (but not the named context itself).
*/
void
MemoryContextReset(MemoryContext context)
{
AssertArg(MemoryContextIsValid(context));
/* save a function call in common case where there are no children */
if (context->firstchild != NULL)
MemoryContextDeleteChildren(context);
/* save a function call if no pallocs since startup or last reset */
if (!context->isReset)
MemoryContextResetOnly(context);
}
/*
* MemoryContextResetOnly
* Release all space allocated within a context.
* Nothing is done to the context's descendant contexts.
*/
void
MemoryContextResetOnly(MemoryContext context)
{
AssertArg(MemoryContextIsValid(context));
/* Nothing to do if no pallocs since startup or last reset */
if (!context->isReset)
{
MemoryContextCallResetCallbacks(context);
(*context->methods->reset) (context);
context->isReset = true;
VALGRIND_DESTROY_MEMPOOL(context);
VALGRIND_CREATE_MEMPOOL(context, 0, false);
}
}
/*
* MemoryContextResetChildren
* Release all space allocated within a context's descendants,
* but don't delete the contexts themselves. The named context
* itself is not touched.
*/
/*
* MemoryContextDelete
* Delete a context and its descendants, and release all space
* allocated therein.
*
* The type-specific delete routine removes all subsidiary storage
* for the context, but we have to delete the context node itself,
* as well as recurse to get the children. We must also delink the
* node from its parent, if it has one.
*/
void
MemoryContextDelete(MemoryContext context)
{
AssertArg(MemoryContextIsValid(context));
/* We had better not be deleting TopMemoryContext ... */
Assert(context != TopMemoryContext);
/* And not CurrentMemoryContext, either */
Assert(context != CurrentMemoryContext);
MemoryContextDeleteChildren(context);
/*
* It's not entirely clear whether 'tis better to do this before or after
* delinking the context; but an error in a callback will likely result in
* leaking the whole context (if it's not a root context) if we do it
* after, so let's do it before.
*/
MemoryContextCallResetCallbacks(context);
/*
* We delink the context from its parent before deleting it, so that if
* there's an error we won't have deleted/busted contexts still attached
* to the context tree. Better a leak than a crash.
*/
MemoryContextSetParent(context, NULL);
(*context->methods->delete_context) (context);
VALGRIND_DESTROY_MEMPOOL(context);
pfree(context);
}
/*
* MemoryContextDeleteChildren
* Delete all the descendants of the named context and release all
* space allocated therein. The named context itself is not touched.
*/
void
MemoryContextDeleteChildren(MemoryContext context)
{
AssertArg(MemoryContextIsValid(context));
/*
* MemoryContextDelete will delink the child from me, so just iterate as
* long as there is a child.
*/
while (context->firstchild != NULL)
MemoryContextDelete(context->firstchild);
}
/*
* MemoryContextRegisterResetCallback
* Register a function to be called before next context reset/delete.
* Such callbacks will be called in reverse order of registration.
*
* The caller is responsible for allocating a MemoryContextCallback struct
* to hold the info about this callback request, and for filling in the
* "func" and "arg" fields in the struct to show what function to call with
* what argument. Typically the callback struct should be allocated within
* the specified context, since that means it will automatically be freed
* when no longer needed.
*
* There is no API for deregistering a callback once registered. If you
* want it to not do anything anymore, adjust the state pointed to by its
* "arg" to indicate that.
*/
/*
* MemoryContextCallResetCallbacks
* Internal function to call all registered callbacks for context.
*/
static void
MemoryContextCallResetCallbacks(MemoryContext context)
{
MemoryContextCallback *cb;
/*
* We pop each callback from the list before calling. That way, if an
* error occurs inside the callback, we won't try to call it a second time
* in the likely event that we reset or delete the context later.
*/
while ((cb = context->reset_cbs) != NULL)
{
context->reset_cbs = cb->next;
(*cb->func) (cb->arg);
}
}
/*
* MemoryContextSetParent
* Change a context to belong to a new parent (or no parent).
*
* We provide this as an API function because it is sometimes useful to
* change a context's lifespan after creation. For example, a context
* might be created underneath a transient context, filled with data,
* and then reparented underneath CacheMemoryContext to make it long-lived.
* In this way no special effort is needed to get rid of the context in case
* a failure occurs before its contents are completely set up.
*
* Callers often assume that this function cannot fail, so don't put any
* elog(ERROR) calls in it.
*
* A possible caller error is to reparent a context under itself, creating
* a loop in the context graph. We assert here that context != new_parent,
* but checking for multi-level loops seems more trouble than it's worth.
*/
void
MemoryContextSetParent(MemoryContext context, MemoryContext new_parent)
{
AssertArg(MemoryContextIsValid(context));
AssertArg(context != new_parent);
/* Fast path if it's got correct parent already */
if (new_parent == context->parent)
return;
/* Delink from existing parent, if any */
if (context->parent)
{
MemoryContext parent = context->parent;
if (context == parent->firstchild)
parent->firstchild = context->nextchild;
else
{
MemoryContext child;
for (child = parent->firstchild; child; child = child->nextchild)
{
if (context == child->nextchild)
{
child->nextchild = context->nextchild;
break;
}
}
}
}
/* And relink */
if (new_parent)
{
AssertArg(MemoryContextIsValid(new_parent));
context->parent = new_parent;
context->nextchild = new_parent->firstchild;
new_parent->firstchild = context;
}
else
{
context->parent = NULL;
context->nextchild = NULL;
}
}
/*
* MemoryContextAllowInCriticalSection
* Allow/disallow allocations in this memory context within a critical
* section.
*
* Normally, memory allocations are not allowed within a critical section,
* because a failure would lead to PANIC. There are a few exceptions to
* that, like allocations related to debugging code that is not supposed to
* be enabled in production. This function can be used to exempt specific
* memory contexts from the assertion in palloc().
*/
void
MemoryContextAllowInCriticalSection(MemoryContext context, bool allow)
{
AssertArg(MemoryContextIsValid(context));
context->allowInCritSection = allow;
}
/*
* GetMemoryChunkSpace
* Given a currently-allocated chunk, determine the total space
* it occupies (including all memory-allocation overhead).
*
* This is useful for measuring the total space occupied by a set of
* allocated chunks.
*/
/*
* GetMemoryChunkContext
* Given a currently-allocated chunk, determine the context
* it belongs to.
*/
/*
* MemoryContextGetParent
* Get the parent context (if any) of the specified context
*/
/*
* MemoryContextIsEmpty
* Is a memory context empty of any allocated space?
*/
/*
* MemoryContextStats
* Print statistics about the named context and all its descendants.
*
* This is just a debugging utility, so it's not fancy. The statistics
* are merely sent to stderr.
*/
void
MemoryContextStats(MemoryContext context)
{
MemoryContextStatsInternal(context, 0);
}
static void
MemoryContextStatsInternal(MemoryContext context, int level)
{
MemoryContext child;
AssertArg(MemoryContextIsValid(context));
(*context->methods->stats) (context, level);
for (child = context->firstchild; child != NULL; child = child->nextchild)
MemoryContextStatsInternal(child, level + 1);
}
/*
* MemoryContextCheck
* Check all chunks in the named context.
*
* This is just a debugging utility, so it's not fancy.
*/
#ifdef MEMORY_CONTEXT_CHECKING
void
MemoryContextCheck(MemoryContext context)
{
MemoryContext child;
AssertArg(MemoryContextIsValid(context));
(*context->methods->check) (context);
for (child = context->firstchild; child != NULL; child = child->nextchild)
MemoryContextCheck(child);
}
#endif
/*
* MemoryContextContains
* Detect whether an allocated chunk of memory belongs to a given
* context or not.
*
* Caution: this test is reliable as long as 'pointer' does point to
* a chunk of memory allocated from *some* context. If 'pointer' points
* at memory obtained in some other way, there is a small chance of a
* false-positive result, since the bits right before it might look like
* a valid chunk header by chance.
*/
/*--------------------
* MemoryContextCreate
* Context-type-independent part of context creation.
*
* This is only intended to be called by context-type-specific
* context creation routines, not by the unwashed masses.
*
* The context creation procedure is a little bit tricky because
* we want to be sure that we don't leave the context tree invalid
* in case of failure (such as insufficient memory to allocate the
* context node itself). The procedure goes like this:
* 1. Context-type-specific routine first calls MemoryContextCreate(),
* passing the appropriate tag/size/methods values (the methods
* pointer will ordinarily point to statically allocated data).
* The parent and name parameters usually come from the caller.
* 2. MemoryContextCreate() attempts to allocate the context node,
* plus space for the name. If this fails we can ereport() with no
* damage done.
* 3. We fill in all of the type-independent MemoryContext fields.
* 4. We call the type-specific init routine (using the methods pointer).
* The init routine is required to make the node minimally valid
* with zero chance of failure --- it can't allocate more memory,
* for example.
* 5. Now we have a minimally valid node that can behave correctly
* when told to reset or delete itself. We link the node to its
* parent (if any), making the node part of the context tree.
* 6. We return to the context-type-specific routine, which finishes
* up type-specific initialization. This routine can now do things
* that might fail (like allocate more memory), so long as it's
* sure the node is left in a state that delete will handle.
*
* This protocol doesn't prevent us from leaking memory if step 6 fails
* during creation of a top-level context, since there's no parent link
* in that case. However, if you run out of memory while you're building
* a top-level context, you might as well go home anyway...
*
* Normally, the context node and the name are allocated from
* TopMemoryContext (NOT from the parent context, since the node must
* survive resets of its parent context!). However, this routine is itself
* used to create TopMemoryContext! If we see that TopMemoryContext is NULL,
* we assume we are creating TopMemoryContext and use malloc() to allocate
* the node.
*
* Note that the name field of a MemoryContext does not point to
* separately-allocated storage, so it should not be freed at context
* deletion.
*--------------------
*/
MemoryContext
MemoryContextCreate(NodeTag tag, Size size,
MemoryContextMethods *methods,
MemoryContext parent,
const char *name)
{
MemoryContext node;
Size needed = size + strlen(name) + 1;
/* creating new memory contexts is not allowed in a critical section */
Assert(CritSectionCount == 0);
/* Get space for node and name */
if (TopMemoryContext != NULL)
{
/* Normal case: allocate the node in TopMemoryContext */
node = (MemoryContext) MemoryContextAlloc(TopMemoryContext,
needed);
}
else
{
/* Special case for startup: use good ol' malloc */
node = (MemoryContext) malloc(needed);
Assert(node != NULL);
}
/* Initialize the node as best we can */
MemSet(node, 0, size);
node->type = tag;
node->methods = methods;
node->parent = NULL; /* for the moment */
node->firstchild = NULL;
node->nextchild = NULL;
node->isReset = true;
node->name = ((char *) node) + size;
strcpy(node->name, name);
/* Type-specific routine finishes any other essential initialization */
(*node->methods->init) (node);
/* OK to link node to parent (if any) */
/* Could use MemoryContextSetParent here, but doesn't seem worthwhile */
if (parent)
{
node->parent = parent;
node->nextchild = parent->firstchild;
parent->firstchild = node;
/* inherit allowInCritSection flag from parent */
node->allowInCritSection = parent->allowInCritSection;
}
VALGRIND_CREATE_MEMPOOL(node, 0, false);
/* Return to type-specific creation routine to finish up */
return node;
}
/*
* MemoryContextAlloc
* Allocate space within the specified context.
*
* This could be turned into a macro, but we'd have to import
* nodes/memnodes.h into postgres.h which seems a bad idea.
*/
void *
MemoryContextAlloc(MemoryContext context, Size size)
{
void *ret;
AssertArg(MemoryContextIsValid(context));
AssertNotInCriticalSection(context);
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
context->isReset = false;
ret = (*context->methods->alloc) (context, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_ALLOC(context, ret, size);
return ret;
}
/*
* MemoryContextAllocZero
* Like MemoryContextAlloc, but clears allocated memory
*
* We could just call MemoryContextAlloc then clear the memory, but this
* is a very common combination, so we provide the combined operation.
*/
void *
MemoryContextAllocZero(MemoryContext context, Size size)
{
void *ret;
AssertArg(MemoryContextIsValid(context));
AssertNotInCriticalSection(context);
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
context->isReset = false;
ret = (*context->methods->alloc) (context, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_ALLOC(context, ret, size);
MemSetAligned(ret, 0, size);
return ret;
}
/*
* MemoryContextAllocZeroAligned
* MemoryContextAllocZero where length is suitable for MemSetLoop
*
* This might seem overly specialized, but it's not because newNode()
* is so often called with compile-time-constant sizes.
*/
void *
MemoryContextAllocZeroAligned(MemoryContext context, Size size)
{
void *ret;
AssertArg(MemoryContextIsValid(context));
AssertNotInCriticalSection(context);
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
context->isReset = false;
ret = (*context->methods->alloc) (context, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_ALLOC(context, ret, size);
MemSetLoop(ret, 0, size);
return ret;
}
/*
* MemoryContextAllocExtended
* Allocate space within the specified context using the given flags.
*/
void *
palloc(Size size)
{
/* duplicates MemoryContextAlloc to avoid increased overhead */
void *ret;
AssertArg(MemoryContextIsValid(CurrentMemoryContext));
AssertNotInCriticalSection(CurrentMemoryContext);
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
CurrentMemoryContext->isReset = false;
ret = (*CurrentMemoryContext->methods->alloc) (CurrentMemoryContext, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_ALLOC(CurrentMemoryContext, ret, size);
return ret;
}
void *
palloc0(Size size)
{
/* duplicates MemoryContextAllocZero to avoid increased overhead */
void *ret;
AssertArg(MemoryContextIsValid(CurrentMemoryContext));
AssertNotInCriticalSection(CurrentMemoryContext);
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
CurrentMemoryContext->isReset = false;
ret = (*CurrentMemoryContext->methods->alloc) (CurrentMemoryContext, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_ALLOC(CurrentMemoryContext, ret, size);
MemSetAligned(ret, 0, size);
return ret;
}
/*
* pfree
* Release an allocated chunk.
*/
void
pfree(void *pointer)
{
MemoryContext context;
/*
* Try to detect bogus pointers handed to us, poorly though we can.
* Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
* allocated chunk.
*/
Assert(pointer != NULL);
Assert(pointer == (void *) MAXALIGN(pointer));
/*
* OK, it's probably safe to look at the chunk header.
*/
context = ((StandardChunkHeader *)
((char *) pointer - STANDARDCHUNKHEADERSIZE))->context;
AssertArg(MemoryContextIsValid(context));
(*context->methods->free_p) (context, pointer);
VALGRIND_MEMPOOL_FREE(context, pointer);
}
/*
* repalloc
* Adjust the size of a previously allocated chunk.
*/
void *
repalloc(void *pointer, Size size)
{
MemoryContext context;
void *ret;
if (!AllocSizeIsValid(size))
elog(ERROR, "invalid memory alloc request size %zu", size);
/*
* Try to detect bogus pointers handed to us, poorly though we can.
* Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
* allocated chunk.
*/
Assert(pointer != NULL);
Assert(pointer == (void *) MAXALIGN(pointer));
/*
* OK, it's probably safe to look at the chunk header.
*/
context = ((StandardChunkHeader *)
((char *) pointer - STANDARDCHUNKHEADERSIZE))->context;
AssertArg(MemoryContextIsValid(context));
AssertNotInCriticalSection(context);
/* isReset must be false already */
Assert(!context->isReset);
ret = (*context->methods->realloc) (context, pointer, size);
if (ret == NULL)
{
MemoryContextStats(TopMemoryContext);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Failed on request of size %zu.", size)));
}
VALGRIND_MEMPOOL_CHANGE(context, pointer, ret, size);
return ret;
}
/*
* MemoryContextAllocHuge
* Allocate (possibly-expansive) space within the specified context.
*
* See considerations in comment at MaxAllocHugeSize.
*/
/*
* repalloc_huge
* Adjust the size of a previously allocated chunk, permitting a large
* value. The previous allocation need not have been "huge".
*/
/*
* MemoryContextStrdup
* Like strdup(), but allocate from the specified context
*/
char *
MemoryContextStrdup(MemoryContext context, const char *string)
{
char *nstr;
Size len = strlen(string) + 1;
nstr = (char *) MemoryContextAlloc(context, len);
memcpy(nstr, string, len);
return nstr;
}
char *
pstrdup(const char *in)
{
return MemoryContextStrdup(CurrentMemoryContext, in);
}
/*
* pnstrdup
* Like pstrdup(), but append null byte to a
* not-necessarily-null-terminated input string.
*/