ipc.c

关系型数据库 Postgresql 6.5.2

	EPRINTF("\nIpcSemaphoreCreate, status %d, returns %d\n",
			*status,
			semId);
	fflush(stdout);
	fflush(stderr);
#endif
	return semId;
}


/****************************************************************************/
/*	 IpcSemaphoreSet()			- sets the initial value of the semaphore	*/
/*																			*/
/*		note: the xxx_return variables are only used for debugging.			*/
/****************************************************************************/
#ifdef NOT_USED
static int	IpcSemaphoreSet_return;

void
IpcSemaphoreSet(int semId, int semno, int value)
{
	int			errStatus;
	union semun semun;

	semun.val = value;
	errStatus = semctl(semId, semno, SETVAL, semun);
	IpcSemaphoreSet_return = errStatus;

	if (errStatus == -1)
	{
		EPRINTF("IpcSemaphoreSet: semctl failed (%s) id=%d",
				strerror(errno), semId);
	}
}

#endif

/****************************************************************************/
/*	 IpcSemaphoreKill(key)		- removes a semaphore						*/
/*																			*/
/****************************************************************************/
void
IpcSemaphoreKill(IpcSemaphoreKey key)
{
	int			semId;
	union semun semun;

	/* kill semaphore if existent */

	semId = semget(key, 0, 0);
	if (semId != -1)
		semctl(semId, 0, IPC_RMID, semun);
}

/****************************************************************************/
/*	 IpcSemaphoreLock(semId, sem, lock) - locks a semaphore					*/
/*																			*/
/*		note: the xxx_return variables are only used for debugging.			*/
/****************************************************************************/
static int	IpcSemaphoreLock_return;

void
IpcSemaphoreLock(IpcSemaphoreId semId, int sem, int lock)
{
	extern int	errno;
	int			errStatus;
	struct sembuf sops;

	sops.sem_op = lock;
	sops.sem_flg = 0;
	sops.sem_num = sem;

	/* ----------------
	 *	Note: if errStatus is -1 and errno == EINTR then it means we
	 *		  returned from the operation prematurely because we were
	 *		  sent a signal.  So we try and lock the semaphore again.
	 *		  I am not certain this is correct, but the semantics aren't
	 *		  clear it fixes problems with parallel abort synchronization,
	 *		  namely that after processing an abort signal, the semaphore
	 *		  call returns with -1 (and errno == EINTR) before it should.
	 *		  -cim 3/28/90
	 * ----------------
	 */
	do
	{
		errStatus = semop(semId, &sops, 1);
	} while (errStatus == -1 && errno == EINTR);

	IpcSemaphoreLock_return = errStatus;

	if (errStatus == -1)
	{
		EPRINTF("IpcSemaphoreLock: semop failed (%s) id=%d",
				strerror(errno), semId);
		proc_exit(255);
	}
}

/****************************************************************************/
/*	 IpcSemaphoreUnlock(semId, sem, lock)		- unlocks a semaphore		*/
/*																			*/
/*		note: the xxx_return variables are only used for debugging.			*/
/****************************************************************************/
static int	IpcSemaphoreUnlock_return;

void
IpcSemaphoreUnlock(IpcSemaphoreId semId, int sem, int lock)
{
	extern int	errno;
	int			errStatus;
	struct sembuf sops;

	sops.sem_op = -lock;
	sops.sem_flg = 0;
	sops.sem_num = sem;


	/* ----------------
	 *	Note: if errStatus is -1 and errno == EINTR then it means we
	 *		  returned from the operation prematurely because we were
	 *		  sent a signal.  So we try and lock the semaphore again.
	 *		  I am not certain this is correct, but the semantics aren't
	 *		  clear it fixes problems with parallel abort synchronization,
	 *		  namely that after processing an abort signal, the semaphore
	 *		  call returns with -1 (and errno == EINTR) before it should.
	 *		  -cim 3/28/90
	 * ----------------
	 */
	do
	{
		errStatus = semop(semId, &sops, 1);
	} while (errStatus == -1 && errno == EINTR);

	IpcSemaphoreUnlock_return = errStatus;

	if (errStatus == -1)
	{
		EPRINTF("IpcSemaphoreUnlock: semop failed (%s) id=%d",
				strerror(errno), semId);
		proc_exit(255);
	}
}

int
IpcSemaphoreGetCount(IpcSemaphoreId semId, int sem)
{
	int			semncnt;
	union semun dummy;			/* for Solaris */

	semncnt = semctl(semId, sem, GETNCNT, dummy);
	return semncnt;
}

int
IpcSemaphoreGetValue(IpcSemaphoreId semId, int sem)
{
	int			semval;
	union semun dummy;			/* for Solaris */

	semval = semctl(semId, sem, GETVAL, dummy);
	return semval;
}

/****************************************************************************/
/*	 IpcMemoryCreate(memKey)												*/
/*																			*/
/*	  - returns the memory identifier, if creation succeeds					*/
/*		returns IpcMemCreationFailed, if failure							*/
/****************************************************************************/

IpcMemoryId
IpcMemoryCreate(IpcMemoryKey memKey, uint32 size, int permission)
{
	IpcMemoryId shmid;

	if (memKey == PrivateIPCKey)
	{
		/* private */
		shmid = PrivateMemoryCreate(memKey, size);
	}
	else
		shmid = shmget(memKey, size, IPC_CREAT | permission);

	if (shmid < 0)
	{
		EPRINTF("IpcMemoryCreate: shmget failed (%s) "
				"key=%d, size=%d, permission=%o",
				strerror(errno), memKey, size, permission);
		return IpcMemCreationFailed;
	}

	/* if (memKey == PrivateIPCKey) */
	on_shmem_exit(IPCPrivateMemoryKill, (caddr_t) shmid);

	return shmid;
}

/****************************************************************************/
/*	IpcMemoryIdGet(memKey, size)	returns the shared memory Id			*/
/*									or IpcMemIdGetFailed					*/
/****************************************************************************/
IpcMemoryId
IpcMemoryIdGet(IpcMemoryKey memKey, uint32 size)
{
	IpcMemoryId shmid;

	shmid = shmget(memKey, size, 0);

	if (shmid < 0)
	{
		EPRINTF("IpcMemoryIdGet: shmget failed (%s) "
				"key=%d, size=%d, permission=%o",
				strerror(errno), memKey, size, 0);
		return IpcMemIdGetFailed;
	}

	return shmid;
}

/****************************************************************************/
/*	IpcMemoryDetach(status, shmaddr)	removes a shared memory segment		*/
/*										from a backend address space		*/
/*	(only called by backends running under the postmaster)					*/
/****************************************************************************/
static void
IpcMemoryDetach(int status, char *shmaddr)
{
	if (shmdt(shmaddr) < 0)
		elog(NOTICE, "IpcMemoryDetach: shmdt(0x%x): %m", shmaddr);
}

/****************************************************************************/
/*	IpcMemoryAttach(memId)	  returns the adress of shared memory			*/
/*							  or IpcMemAttachFailed							*/
/*																			*/
/* CALL IT:  addr = (struct <MemoryStructure> *) IpcMemoryAttach(memId);	*/
/*																			*/
/****************************************************************************/
char *
IpcMemoryAttach(IpcMemoryId memId)
{
	char	   *memAddress;

	if (UsePrivateMemory)
		memAddress = (char *) PrivateMemoryAttach(memId);
	else
		memAddress = (char *) shmat(memId, 0, 0);

	/* if ( *memAddress == -1) { XXX ??? */
	if (memAddress == (char *) -1)
	{
		EPRINTF("IpcMemoryAttach: shmat failed (%s) id=%d",
				strerror(errno), memId);
		return IpcMemAttachFailed;
	}

	if (!UsePrivateMemory)
		on_shmem_exit(IpcMemoryDetach, (caddr_t) memAddress);

	return (char *) memAddress;
}


/****************************************************************************/
/*	IpcMemoryKill(memKey)				removes a shared memory segment		*/
/*	(only called by the postmaster and standalone backends)					*/
/****************************************************************************/
void
IpcMemoryKill(IpcMemoryKey memKey)
{
	IpcMemoryId shmid;

	if (!UsePrivateMemory && (shmid = shmget(memKey, 0, 0)) >= 0)
	{
		if (shmctl(shmid, IPC_RMID, (struct shmid_ds *) NULL) < 0)
		{
			elog(NOTICE, "IpcMemoryKill: shmctl(%d, %d, 0) failed: %m",
				 shmid, IPC_RMID);
		}
	}
}

#ifdef HAS_TEST_AND_SET
/* ------------------
 *	use hardware locks to replace semaphores for sequent machines
 *	to avoid costs of swapping processes and to provide unlimited
 *	supply of locks.
 * ------------------
 */

/* used in spin.c */
SLock	   *SLockArray = NULL;

static SLock **FreeSLockPP;
static int *UnusedSLockIP;
static slock_t *SLockMemoryLock;
static IpcMemoryId SLockMemoryId = -1;

struct ipcdummy
{								/* to get alignment/size right */
	SLock	   *free;
	int			unused;
	slock_t		memlock;
	SLock		slocks[MAX_SPINS + 1];
};

#define SLOCKMEMORYSIZE		sizeof(struct ipcdummy)

void
CreateAndInitSLockMemory(IPCKey key)
{
	int			id;
	SLock	   *slckP;

	SLockMemoryId = IpcMemoryCreate(key,
									SLOCKMEMORYSIZE,
									0700);
	AttachSLockMemory(key);
	*FreeSLockPP = NULL;
	*UnusedSLockIP = (int) FIRSTFREELOCKID;
	for (id = 0; id < (int) FIRSTFREELOCKID; id++)
	{
		slckP = &(SLockArray[id]);
		S_INIT_LOCK(&(slckP->locklock));
		slckP->flag = NOLOCK;
		slckP->nshlocks = 0;
		S_INIT_LOCK(&(slckP->shlock));
		S_INIT_LOCK(&(slckP->exlock));
		S_INIT_LOCK(&(slckP->comlock));
		slckP->next = NULL;
	}
	return;
}

void
AttachSLockMemory(IPCKey key)
{
	struct ipcdummy *slockM;

	if (SLockMemoryId == -1)
		SLockMemoryId = IpcMemoryIdGet(key, SLOCKMEMORYSIZE);
	if (SLockMemoryId == -1)
		elog(FATAL, "SLockMemory not in shared memory");
	slockM = (struct ipcdummy *) IpcMemoryAttach(SLockMemoryId);
	if (slockM == IpcMemAttachFailed)
		elog(FATAL, "AttachSLockMemory: could not attach segment");
	FreeSLockPP = (SLock **) &(slockM->free);
	UnusedSLockIP = (int *) &(slockM->unused);
	SLockMemoryLock = (slock_t *) &(slockM->memlock);
	S_INIT_LOCK(SLockMemoryLock);
	SLockArray = (SLock *) &(slockM->slocks[0]);
	return;
}

#ifdef NOT_USED
bool
LockIsFree(int lockid)
{
	return SLockArray[lockid].flag == NOLOCK;
}

#endif

#endif	 /* HAS_TEST_AND_SET */

#ifdef NOT_USED
static void
IpcConfigTip(void)
{
	fprintf(stderr, "This type of error is usually caused by improper\n");
	fprintf(stderr, "shared memory or System V IPC semaphore configuration.\n");
	fprintf(stderr, "See the FAQ for more detailed information\n");
}

#endif