ipci.c

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/*-------------------------------------------------------------------------
 *
 * ipci.c
 *    POSTGRES inter-process communication initialization code.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/storage/ipc/ipci.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/clog.h"
#include "access/heapam.h"
#include "access/multixact.h"
#include "access/nbtree.h"
#include "access/subtrans.h"
#include "access/twophase.h"
#include "commands/async.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgwriter.h"
#include "postmaster/postmaster.h"
#include "replication/walreceiver.h"
#include "replication/walsender.h"
#include "storage/bufmgr.h"
#include "storage/ipc.h"
#include "storage/pg_shmem.h"
#include "storage/pmsignal.h"
#include "storage/predicate.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/procsignal.h"
#include "storage/sinvaladt.h"
#include "storage/spin.h"


shmem_startup_hook_type shmem_startup_hook = NULL;

static Size total_addin_request = 0;
static bool addin_request_allowed = true;


/*
 * RequestAddinShmemSpace
 *      Request that extra shmem space be allocated for use by
 *      a loadable module.
 *
 * This is only useful if called from the _PG_init hook of a library that
 * is loaded into the postmaster via shared_preload_libraries.  Once
 * shared memory has been allocated, calls will be ignored.  (We could
 * raise an error, but it seems better to make it a no-op, so that
 * libraries containing such calls can be reloaded if needed.)
 */
void
RequestAddinShmemSpace(Size size)
{
    if (IsUnderPostmaster || !addin_request_allowed)
        return;                 /* too late */
    total_addin_request = add_size(total_addin_request, size);
}


/*
 * 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)
{
    if (!IsUnderPostmaster)
    {
        PGShmemHeader *seghdr;
        Size        size;
        int         numSemas;

        /*
         * 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, 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, SUBTRANSShmemSize());
        size = add_size(size, TwoPhaseShmemSize());
        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, WalSndShmemSize());
        size = add_size(size, WalRcvShmemSize());
        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=%lu)",
             (unsigned long) size);

        /*
         * Create the shmem segment
         */
        seghdr = PGSharedMemoryCreate(size, makePrivate, port);

        InitShmemAccess(seghdr);

        /*
         * Create semaphores
         */
        numSemas = ProcGlobalSemas();
        numSemas += SpinlockSemas();
        PGReserveSemaphores(numSemas, port);
    }
    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.
     */
    if (!IsUnderPostmaster)
        CreateLWLocks();

    /*
     * Set up shmem.c index hashtable
     */
    InitShmemIndex();

    /*
     * Set up xlog, clog, and buffers
     */
    XLOGShmemInit();
    CLOGShmemInit();
    SUBTRANSShmemInit();
    MultiXactShmemInit();
    InitBufferPool();

    /*
     * Set up lock manager
     */
    InitLocks();

    /*
     * Set up predicate lock manager
     */
    InitPredicateLocks();

    /*
     * Set up process table
     */
    if (!IsUnderPostmaster)
        InitProcGlobal();
    CreateSharedProcArray();
    CreateSharedBackendStatus();
    TwoPhaseShmemInit();

    /*
     * Set up shared-inval messaging
     */
    CreateSharedInvalidationState();

    /*
     * Set up interprocess signaling mechanisms
     */
    PMSignalShmemInit();
    ProcSignalShmemInit();
    CheckpointerShmemInit();
    AutoVacuumShmemInit();
    WalSndShmemInit();
    WalRcvShmemInit();

    /*
     * Set up other modules that need some shared memory space
     */
    BTreeShmemInit();
    SyncScanShmemInit();
    AsyncShmemInit();

#ifdef EXEC_BACKEND

    /*
     * Alloc the win32 shared backend array
     */
    if (!IsUnderPostmaster)
        ShmemBackendArrayAllocation();
#endif

    /*
     * Now give loadable modules a chance to set up their shmem allocations
     */
    if (shmem_startup_hook)
        shmem_startup_hook();
}