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Postgres95 1.01 Distribution - Virgin Sources
This commit is contained in:
Marc G. Fournier
247
src/backend/storage/ipc/spin.c
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247
src/backend/storage/ipc/spin.c
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/*-------------------------------------------------------------------------
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*
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* spin.c--
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* routines for managing spin locks
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/storage/ipc/Attic/spin.c,v 1.1.1.1 1996/07/09 06:21:55 scrappy Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* POSTGRES has two kinds of locks: semaphores (which put the
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* process to sleep) and spinlocks (which are supposed to be
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* short term locks). Currently both are implemented as SysV
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* semaphores, but presumably this can change if we move to
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* a machine with a test-and-set (TAS) instruction. Its probably
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* a good idea to think about (and allocate) short term and long
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* term semaphores separately anyway.
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*
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* NOTE: These routines are not supposed to be widely used in Postgres.
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* They are preserved solely for the purpose of porting Mark Sullivan's
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* buffer manager to Postgres.
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*/
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#include <errno.h>
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#include "postgres.h"
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#include "storage/ipc.h"
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#include "storage/shmem.h"
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#include "storage/spin.h"
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#include "storage/proc.h"
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#include "utils/elog.h"
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/* globals used in this file */
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IpcSemaphoreId SpinLockId;
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#ifdef HAS_TEST_AND_SET
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/* real spin lock implementations */
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bool
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CreateSpinlocks(IPCKey key)
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{
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/* the spin lock shared memory must have been created by now */
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return(TRUE);
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}
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bool
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AttachSpinLocks(IPCKey key)
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{
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/* the spin lock shared memory must have been attached by now */
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return(TRUE);
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}
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bool
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InitSpinLocks(int init, IPCKey key)
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{
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extern SPINLOCK ShmemLock;
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extern SPINLOCK BindingLock;
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extern SPINLOCK BufMgrLock;
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extern SPINLOCK LockMgrLock;
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extern SPINLOCK ProcStructLock;
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extern SPINLOCK SInvalLock;
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extern SPINLOCK OidGenLockId;
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#ifdef MAIN_MEMORY
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extern SPINLOCK MMCacheLock;
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#endif /* SONY_JUKEBOX */
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/* These six spinlocks have fixed location is shmem */
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ShmemLock = (SPINLOCK) SHMEMLOCKID;
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BindingLock = (SPINLOCK) BINDINGLOCKID;
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BufMgrLock = (SPINLOCK) BUFMGRLOCKID;
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LockMgrLock = (SPINLOCK) LOCKMGRLOCKID;
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ProcStructLock = (SPINLOCK) PROCSTRUCTLOCKID;
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SInvalLock = (SPINLOCK) SINVALLOCKID;
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OidGenLockId = (SPINLOCK) OIDGENLOCKID;
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#ifdef MAIN_MEMORY
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MMCacheLock = (SPINLOCK) MMCACHELOCKID;
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#endif /* MAIN_MEMORY */
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return(TRUE);
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}
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void
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SpinAcquire(SPINLOCK lock)
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{
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ExclusiveLock(lock);
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PROC_INCR_SLOCK(lock);
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}
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void
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SpinRelease(SPINLOCK lock)
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{
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PROC_DECR_SLOCK(lock);
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ExclusiveUnlock(lock);
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}
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bool
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SpinIsLocked(SPINLOCK lock)
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{
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return(!LockIsFree(lock));
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}
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#else /* HAS_TEST_AND_SET */
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/* Spinlocks are implemented using SysV semaphores */
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/*
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* SpinAcquire -- try to grab a spinlock
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*
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* FAILS if the semaphore is corrupted.
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*/
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void
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SpinAcquire(SPINLOCK lock)
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{
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IpcSemaphoreLock(SpinLockId, lock, IpcExclusiveLock);
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PROC_INCR_SLOCK(lock);
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}
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/*
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* SpinRelease -- release a spin lock
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*
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* FAILS if the semaphore is corrupted
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*/
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void
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SpinRelease(SPINLOCK lock)
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{
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Assert(SpinIsLocked(lock))
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PROC_DECR_SLOCK(lock);
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IpcSemaphoreUnlock(SpinLockId, lock, IpcExclusiveLock);
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}
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bool
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SpinIsLocked(SPINLOCK lock)
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{
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int semval;
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semval = IpcSemaphoreGetValue(SpinLockId, lock);
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return(semval < IpcSemaphoreDefaultStartValue);
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}
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/*
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* CreateSpinlocks -- Create a sysV semaphore array for
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* the spinlocks
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*
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*/
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bool
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CreateSpinlocks(IPCKey key)
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{
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int status;
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IpcSemaphoreId semid;
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semid = IpcSemaphoreCreate(key, MAX_SPINS, IPCProtection,
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IpcSemaphoreDefaultStartValue, 1, &status);
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if (status == IpcSemIdExist) {
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IpcSemaphoreKill(key);
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elog(NOTICE,"Destroying old spinlock semaphore");
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semid = IpcSemaphoreCreate(key, MAX_SPINS, IPCProtection,
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IpcSemaphoreDefaultStartValue, 1, &status);
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}
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if (semid >= 0) {
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SpinLockId = semid;
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return(TRUE);
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}
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/* cannot create spinlocks */
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elog(FATAL,"CreateSpinlocks: cannot create spin locks");
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return(FALSE);
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}
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/*
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* Attach to existing spinlock set
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*/
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bool
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AttachSpinLocks(IPCKey key)
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{
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IpcSemaphoreId id;
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id = semget (key, MAX_SPINS, 0);
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if (id < 0) {
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if (errno == EEXIST) {
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/* key is the name of someone else's semaphore */
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elog (FATAL,"AttachSpinlocks: SPIN_KEY belongs to someone else");
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}
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/* cannot create spinlocks */
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elog(FATAL,"AttachSpinlocks: cannot create spin locks");
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return(FALSE);
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}
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SpinLockId = id;
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return(TRUE);
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}
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/*
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* InitSpinLocks -- Spinlock bootstrapping
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*
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* We need several spinlocks for bootstrapping:
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* BindingLock (for the shmem binding table) and
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* ShmemLock (for the shmem allocator), BufMgrLock (for buffer
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* pool exclusive access), LockMgrLock (for the lock table), and
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* ProcStructLock (a spin lock for the shared process structure).
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* If there's a Sony WORM drive attached, we also have a spinlock
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* (SJCacheLock) for it. Same story for the main memory storage mgr.
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*
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*/
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bool
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InitSpinLocks(int init, IPCKey key)
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{
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extern SPINLOCK ShmemLock;
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extern SPINLOCK BindingLock;
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extern SPINLOCK BufMgrLock;
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extern SPINLOCK LockMgrLock;
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extern SPINLOCK ProcStructLock;
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extern SPINLOCK SInvalLock;
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extern SPINLOCK OidGenLockId;
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#ifdef MAIN_MEMORY
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extern SPINLOCK MMCacheLock;
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#endif /* MAIN_MEMORY */
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if (!init || key != IPC_PRIVATE) {
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/* if bootstrap and key is IPC_PRIVATE, it means that we are running
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* backend by itself. no need to attach spinlocks
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*/
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if (! AttachSpinLocks(key)) {
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elog(FATAL,"InitSpinLocks: couldnt attach spin locks");
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return(FALSE);
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}
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}
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/* These five (or six) spinlocks have fixed location is shmem */
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ShmemLock = (SPINLOCK) SHMEMLOCKID;
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BindingLock = (SPINLOCK) BINDINGLOCKID;
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BufMgrLock = (SPINLOCK) BUFMGRLOCKID;
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LockMgrLock = (SPINLOCK) LOCKMGRLOCKID;
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ProcStructLock = (SPINLOCK) PROCSTRUCTLOCKID;
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SInvalLock = (SPINLOCK) SINVALLOCKID;
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OidGenLockId = (SPINLOCK) OIDGENLOCKID;
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#ifdef MAIN_MEMORY
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MMCacheLock = (SPINLOCK) MMCACHELOCKID;
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#endif /* MAIN_MEMORY */
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return(TRUE);
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}
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#endif /* HAS_TEST_AND_SET */
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