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Redesign the patch for allocation of shmem space and LWLocks for add-on

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modules; the first try was not usable in EXEC_BACKEND builds (e.g.,
Windows).  Instead, just provide some entry points to increase the
allocation requests during postmaster start, and provide a dedicated
LWLock that can be used to synchronize allocation operations performed
by backends.  Per discussion with Marc Munro.
This commit is contained in:
Tom Lane
2006-10-15 22:04:08 +00:00
parent a3dff39c53
commit e0dece127d
6 changed files with 73 additions and 259 deletions
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103
src/backend/storage/lmgr/lwlock.c
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@@ -15,7 +15,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.46 2006/10/04 00:29:57 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.47 2006/10/15 22:04:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -30,10 +30,6 @@
#include "storage/spin.h"
static int NumAddinLWLocks(void);
static void AssignAddinLWLocks(void);
/* We use the ShmemLock spinlock to protect LWLockAssign */
extern slock_t *ShmemLock;
@@ -88,6 +84,9 @@ NON_EXEC_STATIC LWLockPadded *LWLockArray = NULL;
static int num_held_lwlocks = 0;
static LWLockId held_lwlocks[MAX_SIMUL_LWLOCKS];
static int lock_addin_request = 0;
static bool lock_addin_request_allowed = true;
#ifdef LWLOCK_STATS
static int counts_for_pid = 0;
static int *sh_acquire_counts;
@@ -95,63 +94,6 @@ static int *ex_acquire_counts;
static int *block_counts;
#endif
/*
* Structures and globals to allow add-ins to register for their own
* lwlocks from the preload-libraries hook.
*/
typedef struct LWLockNode
{
LWLockId *lock;
struct LWLockNode *next;
} LWLockNode;
static LWLockNode *addin_locks = NULL;
static int num_addin_locks = 0;
/*
* RegisterAddinLWLock() --- Allow an andd-in to request a LWLock
* from the preload-libraries hook.
*/
void
RegisterAddinLWLock(LWLockId *lock)
{
LWLockNode *locknode = malloc(sizeof(LWLockNode));
locknode->next = addin_locks;
locknode->lock = lock;
addin_locks = locknode;
num_addin_locks++;
}
/*
* NumAddinLWLocks() --- Return the number of LWLocks requested by add-ins.
*/
static int
NumAddinLWLocks()
{
return num_addin_locks;
}
/*
* AssignAddinLWLocks() --- Assign LWLocks previously requested by add-ins.
*/
static void
AssignAddinLWLocks()
{
LWLockNode *node = addin_locks;
while (node)
{
*(node->lock) = LWLockAssign();
node = node->next;
}
}
#ifdef LOCK_DEBUG
bool Trace_lwlocks = false;
@@ -231,16 +173,38 @@ NumLWLocks(void)
/* multixact.c needs two SLRU areas */
numLocks += NUM_MXACTOFFSET_BUFFERS + NUM_MXACTMEMBER_BUFFERS;
/* Leave a few extra for use by user-defined modules. */
numLocks += NUM_USER_DEFINED_LWLOCKS;
/* Add the number that have been explicitly requested by add-ins. */
numLocks += NumAddinLWLocks();
/*
* Add any requested by loadable modules; for backwards-compatibility
* reasons, allocate at least NUM_USER_DEFINED_LWLOCKS of them even
* if there are no explicit requests.
*/
lock_addin_request_allowed = false;
numLocks += Max(lock_addin_request, NUM_USER_DEFINED_LWLOCKS);
return numLocks;
}
/*
* RequestAddinLWLocks
* Request that extra LWLocks be allocated for use by
* a loadable module.
*
* This is only useful if called from the _PG_init hook of a library that
* is loaded into the postmaster via shared_preload_libraries. Once
* shared memory has been allocated, calls will be ignored. (We could
* raise an error, but it seems better to make it a no-op, so that
* libraries containing such calls can be reloaded if needed.)
*/
void
RequestAddinLWLocks(int n)
{
if (IsUnderPostmaster || !lock_addin_request_allowed)
return; /* too late */
lock_addin_request += n;
}
/*
* Compute shmem space needed for LWLocks.
*/
@@ -304,11 +268,6 @@ CreateLWLocks(void)
LWLockCounter = (int *) ((char *) LWLockArray - 2 * sizeof(int));
LWLockCounter[0] = (int) NumFixedLWLocks;
LWLockCounter[1] = numLocks;
/*
* Allocate LWLocks for those add-ins that have explicitly requested them.
*/
AssignAddinLWLocks();
}