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/*-------------------------------------------------------------------------
*
* spin.c--
* routines for managing spin locks
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/Attic/spin.c,v 1.1.1.1 1996/07/09 06:21:55 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
/*
* POSTGRES has two kinds of locks: semaphores (which put the
* process to sleep) and spinlocks (which are supposed to be
* short term locks). Currently both are implemented as SysV
* semaphores, but presumably this can change if we move to
* a machine with a test-and-set (TAS) instruction. Its probably
* a good idea to think about (and allocate) short term and long
* term semaphores separately anyway.
*
* NOTE: These routines are not supposed to be widely used in Postgres.
* They are preserved solely for the purpose of porting Mark Sullivan's
* buffer manager to Postgres.
*/
#include <errno.h>
#include "postgres.h"
#include "storage/ipc.h"
#include "storage/shmem.h"
#include "storage/spin.h"
#include "storage/proc.h"
#include "utils/elog.h"
/* globals used in this file */
IpcSemaphoreId SpinLockId;
#ifdef HAS_TEST_AND_SET
/* real spin lock implementations */
bool
CreateSpinlocks(IPCKey key)
{
/* the spin lock shared memory must have been created by now */
return(TRUE);
}
bool
AttachSpinLocks(IPCKey key)
{
/* the spin lock shared memory must have been attached by now */
return(TRUE);
}
bool
InitSpinLocks(int init, IPCKey key)
{
extern SPINLOCK ShmemLock;
extern SPINLOCK BindingLock;
extern SPINLOCK BufMgrLock;
extern SPINLOCK LockMgrLock;
extern SPINLOCK ProcStructLock;
extern SPINLOCK SInvalLock;
extern SPINLOCK OidGenLockId;
#ifdef MAIN_MEMORY
extern SPINLOCK MMCacheLock;
#endif /* SONY_JUKEBOX */
/* These six spinlocks have fixed location is shmem */
ShmemLock = (SPINLOCK) SHMEMLOCKID;
BindingLock = (SPINLOCK) BINDINGLOCKID;
BufMgrLock = (SPINLOCK) BUFMGRLOCKID;
LockMgrLock = (SPINLOCK) LOCKMGRLOCKID;
ProcStructLock = (SPINLOCK) PROCSTRUCTLOCKID;
SInvalLock = (SPINLOCK) SINVALLOCKID;
OidGenLockId = (SPINLOCK) OIDGENLOCKID;
#ifdef MAIN_MEMORY
MMCacheLock = (SPINLOCK) MMCACHELOCKID;
#endif /* MAIN_MEMORY */
return(TRUE);
}
void
SpinAcquire(SPINLOCK lock)
{
ExclusiveLock(lock);
PROC_INCR_SLOCK(lock);
}
void
SpinRelease(SPINLOCK lock)
{
PROC_DECR_SLOCK(lock);
ExclusiveUnlock(lock);
}
bool
SpinIsLocked(SPINLOCK lock)
{
return(!LockIsFree(lock));
}
#else /* HAS_TEST_AND_SET */
/* Spinlocks are implemented using SysV semaphores */
/*
* SpinAcquire -- try to grab a spinlock
*
* FAILS if the semaphore is corrupted.
*/
void
SpinAcquire(SPINLOCK lock)
{
IpcSemaphoreLock(SpinLockId, lock, IpcExclusiveLock);
PROC_INCR_SLOCK(lock);
}
/*
* SpinRelease -- release a spin lock
*
* FAILS if the semaphore is corrupted
*/
void
SpinRelease(SPINLOCK lock)
{
Assert(SpinIsLocked(lock))
PROC_DECR_SLOCK(lock);
IpcSemaphoreUnlock(SpinLockId, lock, IpcExclusiveLock);
}
bool
SpinIsLocked(SPINLOCK lock)
{
int semval;
semval = IpcSemaphoreGetValue(SpinLockId, lock);
return(semval < IpcSemaphoreDefaultStartValue);
}
/*
* CreateSpinlocks -- Create a sysV semaphore array for
* the spinlocks
*
*/
bool
CreateSpinlocks(IPCKey key)
{
int status;
IpcSemaphoreId semid;
semid = IpcSemaphoreCreate(key, MAX_SPINS, IPCProtection,
IpcSemaphoreDefaultStartValue, 1, &status);
if (status == IpcSemIdExist) {
IpcSemaphoreKill(key);
elog(NOTICE,"Destroying old spinlock semaphore");
semid = IpcSemaphoreCreate(key, MAX_SPINS, IPCProtection,
IpcSemaphoreDefaultStartValue, 1, &status);
}
if (semid >= 0) {
SpinLockId = semid;
return(TRUE);
}
/* cannot create spinlocks */
elog(FATAL,"CreateSpinlocks: cannot create spin locks");
return(FALSE);
}
/*
* Attach to existing spinlock set
*/
bool
AttachSpinLocks(IPCKey key)
{
IpcSemaphoreId id;
id = semget (key, MAX_SPINS, 0);
if (id < 0) {
if (errno == EEXIST) {
/* key is the name of someone else's semaphore */
elog (FATAL,"AttachSpinlocks: SPIN_KEY belongs to someone else");
}
/* cannot create spinlocks */
elog(FATAL,"AttachSpinlocks: cannot create spin locks");
return(FALSE);
}
SpinLockId = id;
return(TRUE);
}
/*
* InitSpinLocks -- Spinlock bootstrapping
*
* We need several spinlocks for bootstrapping:
* BindingLock (for the shmem binding table) and
* ShmemLock (for the shmem allocator), BufMgrLock (for buffer
* pool exclusive access), LockMgrLock (for the lock table), and
* ProcStructLock (a spin lock for the shared process structure).
* If there's a Sony WORM drive attached, we also have a spinlock
* (SJCacheLock) for it. Same story for the main memory storage mgr.
*
*/
bool
InitSpinLocks(int init, IPCKey key)
{
extern SPINLOCK ShmemLock;
extern SPINLOCK BindingLock;
extern SPINLOCK BufMgrLock;
extern SPINLOCK LockMgrLock;
extern SPINLOCK ProcStructLock;
extern SPINLOCK SInvalLock;
extern SPINLOCK OidGenLockId;
#ifdef MAIN_MEMORY
extern SPINLOCK MMCacheLock;
#endif /* MAIN_MEMORY */
if (!init || key != IPC_PRIVATE) {
/* if bootstrap and key is IPC_PRIVATE, it means that we are running
* backend by itself. no need to attach spinlocks
*/
if (! AttachSpinLocks(key)) {
elog(FATAL,"InitSpinLocks: couldnt attach spin locks");
return(FALSE);
}
}
/* These five (or six) spinlocks have fixed location is shmem */
ShmemLock = (SPINLOCK) SHMEMLOCKID;
BindingLock = (SPINLOCK) BINDINGLOCKID;
BufMgrLock = (SPINLOCK) BUFMGRLOCKID;
LockMgrLock = (SPINLOCK) LOCKMGRLOCKID;
ProcStructLock = (SPINLOCK) PROCSTRUCTLOCKID;
SInvalLock = (SPINLOCK) SINVALLOCKID;
OidGenLockId = (SPINLOCK) OIDGENLOCKID;
#ifdef MAIN_MEMORY
MMCacheLock = (SPINLOCK) MMCACHELOCKID;
#endif /* MAIN_MEMORY */
return(TRUE);
}
#endif /* HAS_TEST_AND_SET */
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