/*
* 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);
}
/*
* 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);
}
/*
* CreateSharedMemoryAndSemaphores
* Creates and initializes shared memory and semaphores.
*
* This is called by the postmaster or by a standalone backend.
* It is also called by a backend forked from the postmaster in the
* EXEC_BACKEND case. In the latter case, the shared memory segment
* already exists and has been physically attached to, but we have to
* initialize pointers in local memory that reference the shared structures,
* because we didn't inherit the correct pointer values from the postmaster
* as we do in the fork() scenario. The easiest way to do that is to run
* through the same code as before. (Note that the called routines mostly
* check IsUnderPostmaster, rather than EXEC_BACKEND, to detect this case.
* This is a bit code-wasteful and could be cleaned up.)
*
* If "makePrivate" is true then we only need private memory, not shared
* memory. This is true for a standalone backend, false for a postmaster.
*/
void
CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
{
PGShmemHeader *shim = NULL;
if (!IsUnderPostmaster)
{
PGShmemHeader *seghdr;
Size size;
int numSemas;
/* Compute number of semaphores we'll need */
numSemas = ProcGlobalSemas();
numSemas += SpinlockSemas();
/*
* Size of the Postgres shared-memory block is estimated via
* moderately-accurate estimates for the big hogs, plus 100K for the
* stuff that's too small to bother with estimating.
*
* We take some care during this phase to ensure that the total size
* request doesn't overflow size_t. If this gets through, we don't
* need to be so careful during the actual allocation phase.
*/
size = 100000;
size = add_size(size, PGSemaphoreShmemSize(numSemas));
size = add_size(size, SpinlockSemaSize());
size = add_size(size, hash_estimate_size(SHMEM_INDEX_SIZE,
sizeof(ShmemIndexEnt)));
size = add_size(size, BufferShmemSize());
size = add_size(size, LockShmemSize());
size = add_size(size, PredicateLockShmemSize());
size = add_size(size, ProcGlobalShmemSize());
size = add_size(size, XLOGShmemSize());
size = add_size(size, CLOGShmemSize());
size = add_size(size, CommitTsShmemSize());
size = add_size(size, SUBTRANSShmemSize());
size = add_size(size, TwoPhaseShmemSize());
size = add_size(size, BackgroundWorkerShmemSize());
size = add_size(size, MultiXactShmemSize());
size = add_size(size, LWLockShmemSize());
size = add_size(size, ProcArrayShmemSize());
size = add_size(size, BackendStatusShmemSize());
size = add_size(size, SInvalShmemSize());
size = add_size(size, PMSignalShmemSize());
size = add_size(size, ProcSignalShmemSize());
size = add_size(size, CheckpointerShmemSize());
size = add_size(size, AutoVacuumShmemSize());
size = add_size(size, ReplicationSlotsShmemSize());
size = add_size(size, ReplicationOriginShmemSize());
size = add_size(size, WalSndShmemSize());
size = add_size(size, WalRcvShmemSize());
size = add_size(size, ApplyLauncherShmemSize());
size = add_size(size, SnapMgrShmemSize());
size = add_size(size, BTreeShmemSize());
size = add_size(size, SyncScanShmemSize());
size = add_size(size, AsyncShmemSize());
#ifdef EXEC_BACKEND
size = add_size(size, ShmemBackendArraySize());
#endif
/* freeze the addin request size and include it */
addin_request_allowed = false;
size = add_size(size, total_addin_request);
/* might as well round it off to a multiple of a typical page size */
size = add_size(size, 8192 - (size % 8192));
elog(DEBUG3, "invoking IpcMemoryCreate(size=%zu)", size);
/*
* Create the shmem segment
*/
seghdr = PGSharedMemoryCreate(size, makePrivate, port, &shim);
InitShmemAccess(seghdr);
/*
* Create semaphores
*/
PGReserveSemaphores(numSemas, port);
/*
* If spinlocks are disabled, initialize emulation layer (which
* depends on semaphores, so the order is important here).
*/
#ifndef HAVE_SPINLOCKS
SpinlockSemaInit();
#endif
}
else
{
/*
* We are reattaching to an existing shared memory segment. This
* should only be reached in the EXEC_BACKEND case, and even then only
* with makePrivate == false.
*/
#ifdef EXEC_BACKEND
Assert(!makePrivate);
#else
elog(PANIC, "should be attached to shared memory already");
#endif
}
/*
* Set up shared memory allocation mechanism
*/
if (!IsUnderPostmaster)
InitShmemAllocation();
/*
* Now initialize LWLocks, which do shared memory allocation and are
* needed for InitShmemIndex.
*/
CreateLWLocks();
/*
* Set up shmem.c index hashtable
*/
InitShmemIndex();
/*
* Set up xlog, clog, and buffers
*/
XLOGShmemInit();
CLOGShmemInit();
CommitTsShmemInit();
SUBTRANSShmemInit();
MultiXactShmemInit();
InitBufferPool();
/*
* Set up lock manager
*/
InitLocks();
/*
* Set up predicate lock manager
*/
InitPredicateLocks();
/*
* Set up process table
*/
if (!IsUnderPostmaster)
InitProcGlobal();
CreateSharedProcArray();
CreateSharedBackendStatus();
TwoPhaseShmemInit();
BackgroundWorkerShmemInit();
/*
* Set up shared-inval messaging
*/
CreateSharedInvalidationState();
/*
* Set up interprocess signaling mechanisms
*/
PMSignalShmemInit();
ProcSignalShmemInit();
CheckpointerShmemInit();
AutoVacuumShmemInit();
ReplicationSlotsShmemInit();
ReplicationOriginShmemInit();
WalSndShmemInit();
WalRcvShmemInit();
ApplyLauncherShmemInit();
/*
* Set up other modules that need some shared memory space
*/
SnapMgrInit();
BTreeShmemInit();
SyncScanShmemInit();
AsyncShmemInit();
#ifdef EXEC_BACKEND
/*
* Alloc the win32 shared backend array
*/
if (!IsUnderPostmaster)
ShmemBackendArrayAllocation();
#endif
/* Initialize dynamic shared memory facilities. */
if (!IsUnderPostmaster)
dsm_postmaster_startup(shim);
/*
* Now give loadable modules a chance to set up their shmem allocations
*/
if (shmem_startup_hook)
shmem_startup_hook();
}
