/*
* InitShmemAllocation() --- set up shared-memory space allocation.
*
* This should be called only in the postmaster or a standalone backend.
*/
void
InitShmemAllocation(void)
{
PGShmemHeader *shmhdr = ShmemSegHdr;
char *aligned;
Assert(shmhdr != NULL);
/*
* Initialize the spinlock used by ShmemAlloc. We must use
* ShmemAllocUnlocked, since obviously ShmemAlloc can't be called yet.
*/
ShmemLock = (slock_t *) ShmemAllocUnlocked(sizeof(slock_t));
SpinLockInit(ShmemLock);
/*
* Allocations after this point should go through ShmemAlloc, which
* expects to allocate everything on cache line boundaries. Make sure the
* first allocation begins on a cache line boundary.
*/
aligned = (char *)
(CACHELINEALIGN((((char *) shmhdr) + shmhdr->freeoffset)));
shmhdr->freeoffset = aligned - (char *) shmhdr;
/* ShmemIndex can't be set up yet (need LWLocks first) */
shmhdr->index = NULL;
ShmemIndex = (HTAB *) NULL;
/*
* Initialize ShmemVariableCache for transaction manager. (This doesn't
* really belong here, but not worth moving.)
*/
ShmemVariableCache = (VariableCache)
ShmemAlloc(sizeof(*ShmemVariableCache));
memset(ShmemVariableCache, 0, sizeof(*ShmemVariableCache));
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for SysV, we use
* it to generate the starting semaphore key). In a standalone backend,
* zero will be passed.
*
* In the SysV implementation, we acquire semaphore sets on-demand; the
* maxSemas parameter is just used to size the arrays. There is an array
* of PGSemaphoreData structs in shared memory, and a postmaster-local array
* with one entry per SysV semaphore set, which we use for releasing the
* semaphore sets when done. (This design ensures that postmaster shutdown
* doesn't rely on the contents of shared memory, which a failed backend might
* have clobbered.)
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
/*
* We must use ShmemAllocUnlocked(), since the spinlock protecting
* ShmemAlloc() won't be ready yet. (This ordering is necessary when we
* are emulating spinlocks with semaphores.)
*/
sharedSemas = (PGSemaphore)
ShmemAllocUnlocked(PGSemaphoreShmemSize(maxSemas));
numSharedSemas = 0;
maxSharedSemas = maxSemas;
maxSemaSets = (maxSemas + SEMAS_PER_SET - 1) / SEMAS_PER_SET;
mySemaSets = (IpcSemaphoreId *)
malloc(maxSemaSets * sizeof(IpcSemaphoreId));
if (mySemaSets == NULL)
elog(PANIC, "out of memory");
numSemaSets = 0;
nextSemaKey = port * 1000;
nextSemaNumber = SEMAS_PER_SET; /* force sema set alloc on 1st call */
on_shmem_exit(ReleaseSemaphores, 0);
}
/*
* PGReserveSemaphores --- initialize semaphore support
*
* This is called during postmaster start or shared memory reinitialization.
* It should do whatever is needed to be able to support up to maxSemas
* subsequent PGSemaphoreCreate calls. Also, if any system resources
* are acquired here or in PGSemaphoreCreate, register an on_shmem_exit
* callback to release them.
*
* The port number is passed for possible use as a key (for Posix, we use
* it to generate the starting semaphore name). In a standalone backend,
* zero will be passed.
*
* In the Posix implementation, we acquire semaphores on-demand; the
* maxSemas parameter is just used to size the arrays. For unnamed
* semaphores, there is an array of PGSemaphoreData structs in shared memory.
* For named semaphores, we keep a postmaster-local array of sem_t pointers,
* which we use for releasing the semphores when done.
* (This design minimizes the dependency of postmaster shutdown on the
* contents of shared memory, which a failed backend might have clobbered.
* We can't do much about the possibility of sem_destroy() crashing, but
* we don't have to expose the counters to other processes.)
*/
void
PGReserveSemaphores(int maxSemas, int port)
{
#ifdef USE_NAMED_POSIX_SEMAPHORES
mySemPointers = (sem_t **) malloc(maxSemas * sizeof(sem_t *));
if (mySemPointers == NULL)
elog(PANIC, "out of memory");
#else
/*
* We must use ShmemAllocUnlocked(), since the spinlock protecting
* ShmemAlloc() won't be ready yet. (This ordering is necessary when we
* are emulating spinlocks with semaphores.)
*/
sharedSemas = (PGSemaphore)
ShmemAllocUnlocked(PGSemaphoreShmemSize(maxSemas));
#endif
numSems = 0;
maxSems = maxSemas;
nextSemKey = port * 1000;
on_shmem_exit(ReleaseSemaphores, 0);
}
