bgworker.c File Reference

#include "postgres.h"
#include "access/parallel.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "port/atomics.h"
#include "postmaster/bgworker_internals.h"
#include "postmaster/interrupt.h"
#include "postmaster/postmaster.h"
#include "replication/logicallauncher.h"
#include "replication/logicalworker.h"
#include "storage/dsm.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/lwlock.h"
#include "storage/pg_shmem.h"
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "storage/procsignal.h"
#include "storage/shmem.h"
#include "tcop/tcopprot.h"
#include "utils/ascii.h"
#include "utils/ps_status.h"
#include "utils/timeout.h"

Include dependency graph for bgworker.c:

Go to the source code of this file.

Data Structures
struct	BackgroundWorkerSlot
struct	BackgroundWorkerArray
struct	BackgroundWorkerHandle

Typedefs
typedef struct BackgroundWorkerSlot	BackgroundWorkerSlot
typedef struct BackgroundWorkerArray	BackgroundWorkerArray

Functions
static bgworker_main_type	LookupBackgroundWorkerFunction (const char *libraryname, const char *funcname)
Size	BackgroundWorkerShmemSize (void)
void	BackgroundWorkerShmemInit (void)
static RegisteredBgWorker *	FindRegisteredWorkerBySlotNumber (int slotno)
void	BackgroundWorkerStateChange (bool allow_new_workers)
void	ForgetBackgroundWorker (slist_mutable_iter *cur)
void	ReportBackgroundWorkerPID (RegisteredBgWorker *rw)
void	ReportBackgroundWorkerExit (slist_mutable_iter *cur)
void	BackgroundWorkerStopNotifications (pid_t pid)
void	ForgetUnstartedBackgroundWorkers (void)
void	ResetBackgroundWorkerCrashTimes (void)
static bool	SanityCheckBackgroundWorker (BackgroundWorker *worker, int elevel)
static void	bgworker_die (SIGNAL_ARGS)
void	StartBackgroundWorker (void)
void	RegisterBackgroundWorker (BackgroundWorker *worker)
bool	RegisterDynamicBackgroundWorker (BackgroundWorker *worker, BackgroundWorkerHandle **handle)
BgwHandleStatus	GetBackgroundWorkerPid (BackgroundWorkerHandle *handle, pid_t *pidp)
BgwHandleStatus	WaitForBackgroundWorkerStartup (BackgroundWorkerHandle *handle, pid_t *pidp)
BgwHandleStatus	WaitForBackgroundWorkerShutdown (BackgroundWorkerHandle *handle)
void	TerminateBackgroundWorker (BackgroundWorkerHandle *handle)
const char *	GetBackgroundWorkerTypeByPid (pid_t pid)

Variables
slist_head	BackgroundWorkerList = SLIST_STATIC_INIT(BackgroundWorkerList)
static BackgroundWorkerArray *	BackgroundWorkerData
struct {
const char *   fn_name
bgworker_main_type   fn_addr
}	InternalBGWorkers []

Typedef Documentation

BackgroundWorkerArray

typedef struct BackgroundWorkerArray BackgroundWorkerArray

BackgroundWorkerSlot

typedef struct BackgroundWorkerSlot BackgroundWorkerSlot

Function Documentation

BackgroundWorkerShmemInit()

void BackgroundWorkerShmemInit

(

void

)

Definition at line 161 of file bgworker.c.

{
    bool        found;
 
    BackgroundWorkerData = ShmemInitStruct("Background Worker Data",
                                           BackgroundWorkerShmemSize(),
                                           &found);
    if (!IsUnderPostmaster)
    {
        slist_iter  siter;
        int         slotno = 0;
 
        BackgroundWorkerData->total_slots = max_worker_processes;
        BackgroundWorkerData->parallel_register_count = 0;
        BackgroundWorkerData->parallel_terminate_count = 0;
 
        /*
         * Copy contents of worker list into shared memory.  Record the shared
         * memory slot assigned to each worker.  This ensures a 1-to-1
         * correspondence between the postmaster's private list and the array
         * in shared memory.
         */
        slist_foreach(siter, &BackgroundWorkerList)
        {
            BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
            RegisteredBgWorker *rw;
 
            rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
            Assert(slotno < max_worker_processes);
            slot->in_use = true;
            slot->terminate = false;
            slot->pid = InvalidPid;
            slot->generation = 0;
            rw->rw_shmem_slot = slotno;
            rw->rw_worker.bgw_notify_pid = 0;   /* might be reinit after crash */
            memcpy(&slot->worker, &rw->rw_worker, sizeof(BackgroundWorker));
            ++slotno;
        }
 
        /*
         * Mark any remaining slots as not in use.
         */
        while (slotno < max_worker_processes)
        {
            BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
 
            slot->in_use = false;
            ++slotno;
        }
    }
    else
        Assert(found);
}

References Assert(), BackgroundWorkerData, BackgroundWorkerList, BackgroundWorkerShmemSize(), BackgroundWorker::bgw_notify_pid, slist_iter::cur, BackgroundWorkerSlot::generation, BackgroundWorkerSlot::in_use, InvalidPid, IsUnderPostmaster, max_worker_processes, BackgroundWorkerArray::parallel_register_count, BackgroundWorkerArray::parallel_terminate_count, BackgroundWorkerSlot::pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, ShmemInitStruct(), slist_container, slist_foreach, BackgroundWorkerArray::slot, BackgroundWorkerSlot::terminate, BackgroundWorkerArray::total_slots, and BackgroundWorkerSlot::worker.

Referenced by CreateSharedMemoryAndSemaphores().

BackgroundWorkerShmemSize()

Size BackgroundWorkerShmemSize

(

void

)

Definition at line 145 of file bgworker.c.

{
    Size        size;
 
    /* Array of workers is variably sized. */
    size = offsetof(BackgroundWorkerArray, slot);
    size = add_size(size, mul_size(max_worker_processes,
                                   sizeof(BackgroundWorkerSlot)));
 
    return size;
}

References add_size(), max_worker_processes, and mul_size().

Referenced by BackgroundWorkerShmemInit(), and CalculateShmemSize().

BackgroundWorkerStateChange()

void BackgroundWorkerStateChange

(

bool

allow_new_workers

)

Definition at line 245 of file bgworker.c.

{
    int         slotno;
 
    /*
     * The total number of slots stored in shared memory should match our
     * notion of max_worker_processes.  If it does not, something is very
     * wrong.  Further down, we always refer to this value as
     * max_worker_processes, in case shared memory gets corrupted while we're
     * looping.
     */
    if (max_worker_processes != BackgroundWorkerData->total_slots)
    {
        ereport(LOG,
                (errmsg("inconsistent background worker state (max_worker_processes=%d, total_slots=%d)",
                        max_worker_processes,
                        BackgroundWorkerData->total_slots)));
        return;
    }
 
    /*
     * Iterate through slots, looking for newly-registered workers or workers
     * who must die.
     */
    for (slotno = 0; slotno < max_worker_processes; ++slotno)
    {
        BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
        RegisteredBgWorker *rw;
 
        if (!slot->in_use)
            continue;
 
        /*
         * Make sure we don't see the in_use flag before the updated slot
         * contents.
         */
        pg_read_barrier();
 
        /* See whether we already know about this worker. */
        rw = FindRegisteredWorkerBySlotNumber(slotno);
        if (rw != NULL)
        {
            /*
             * In general, the worker data can't change after it's initially
             * registered.  However, someone can set the terminate flag.
             */
            if (slot->terminate && !rw->rw_terminate)
            {
                rw->rw_terminate = true;
                if (rw->rw_pid != 0)
                    kill(rw->rw_pid, SIGTERM);
                else
                {
                    /* Report never-started, now-terminated worker as dead. */
                    ReportBackgroundWorkerPID(rw);
                }
            }
            continue;
        }
 
        /*
         * If we aren't allowing new workers, then immediately mark it for
         * termination; the next stanza will take care of cleaning it up.
         * Doing this ensures that any process waiting for the worker will get
         * awoken, even though the worker will never be allowed to run.
         */
        if (!allow_new_workers)
            slot->terminate = true;
 
        /*
         * If the worker is marked for termination, we don't need to add it to
         * the registered workers list; we can just free the slot. However, if
         * bgw_notify_pid is set, the process that registered the worker may
         * need to know that we've processed the terminate request, so be sure
         * to signal it.
         */
        if (slot->terminate)
        {
            int         notify_pid;
 
            /*
             * We need a memory barrier here to make sure that the load of
             * bgw_notify_pid and the update of parallel_terminate_count
             * complete before the store to in_use.
             */
            notify_pid = slot->worker.bgw_notify_pid;
            if ((slot->worker.bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
                BackgroundWorkerData->parallel_terminate_count++;
            slot->pid = 0;
 
            pg_memory_barrier();
            slot->in_use = false;
 
            if (notify_pid != 0)
                kill(notify_pid, SIGUSR1);
 
            continue;
        }
 
        /*
         * Copy the registration data into the registered workers list.
         */
        rw = malloc(sizeof(RegisteredBgWorker));
        if (rw == NULL)
        {
            ereport(LOG,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of memory")));
            return;
        }
 
        /*
         * Copy strings in a paranoid way.  If shared memory is corrupted, the
         * source data might not even be NUL-terminated.
         */
        ascii_safe_strlcpy(rw->rw_worker.bgw_name,
                           slot->worker.bgw_name, BGW_MAXLEN);
        ascii_safe_strlcpy(rw->rw_worker.bgw_type,
                           slot->worker.bgw_type, BGW_MAXLEN);
        ascii_safe_strlcpy(rw->rw_worker.bgw_library_name,
                           slot->worker.bgw_library_name, BGW_MAXLEN);
        ascii_safe_strlcpy(rw->rw_worker.bgw_function_name,
                           slot->worker.bgw_function_name, BGW_MAXLEN);
 
        /*
         * Copy various fixed-size fields.
         *
         * flags, start_time, and restart_time are examined by the postmaster,
         * but nothing too bad will happen if they are corrupted.  The
         * remaining fields will only be examined by the child process.  It
         * might crash, but we won't.
         */
        rw->rw_worker.bgw_flags = slot->worker.bgw_flags;
        rw->rw_worker.bgw_start_time = slot->worker.bgw_start_time;
        rw->rw_worker.bgw_restart_time = slot->worker.bgw_restart_time;
        rw->rw_worker.bgw_main_arg = slot->worker.bgw_main_arg;
        memcpy(rw->rw_worker.bgw_extra, slot->worker.bgw_extra, BGW_EXTRALEN);
 
        /*
         * Copy the PID to be notified about state changes, but only if the
         * postmaster knows about a backend with that PID.  It isn't an error
         * if the postmaster doesn't know about the PID, because the backend
         * that requested the worker could have died (or been killed) just
         * after doing so.  Nonetheless, at least until we get some experience
         * with how this plays out in the wild, log a message at a relative
         * high debug level.
         */
        rw->rw_worker.bgw_notify_pid = slot->worker.bgw_notify_pid;
        if (!PostmasterMarkPIDForWorkerNotify(rw->rw_worker.bgw_notify_pid))
        {
            elog(DEBUG1, "worker notification PID %d is not valid",
                 (int) rw->rw_worker.bgw_notify_pid);
            rw->rw_worker.bgw_notify_pid = 0;
        }
 
        /* Initialize postmaster bookkeeping. */
        rw->rw_backend = NULL;
        rw->rw_pid = 0;
        rw->rw_child_slot = 0;
        rw->rw_crashed_at = 0;
        rw->rw_shmem_slot = slotno;
        rw->rw_terminate = false;
 
        /* Log it! */
        ereport(DEBUG1,
                (errmsg_internal("registering background worker \"%s\"",
                                 rw->rw_worker.bgw_name)));
 
        slist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
    }
}

References ascii_safe_strlcpy(), BackgroundWorkerData, BackgroundWorkerList, BackgroundWorker::bgw_extra, BGW_EXTRALEN, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BGW_MAXLEN, BackgroundWorker::bgw_name, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, BGWORKER_CLASS_PARALLEL, DEBUG1, elog(), ereport, errcode(), errmsg(), errmsg_internal(), FindRegisteredWorkerBySlotNumber(), BackgroundWorkerSlot::in_use, kill, LOG, malloc, max_worker_processes, BackgroundWorkerArray::parallel_terminate_count, pg_memory_barrier, pg_read_barrier, BackgroundWorkerSlot::pid, PostmasterMarkPIDForWorkerNotify(), ReportBackgroundWorkerPID(), RegisteredBgWorker::rw_backend, RegisteredBgWorker::rw_child_slot, RegisteredBgWorker::rw_crashed_at, RegisteredBgWorker::rw_lnode, RegisteredBgWorker::rw_pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_terminate, RegisteredBgWorker::rw_worker, SIGUSR1, slist_push_head(), BackgroundWorkerArray::slot, BackgroundWorkerSlot::terminate, BackgroundWorkerArray::total_slots, and BackgroundWorkerSlot::worker.

Referenced by process_pm_pmsignal().

BackgroundWorkerStopNotifications()

void BackgroundWorkerStopNotifications

(

pid_t

pid

)

Definition at line 517 of file bgworker.c.

{
    slist_iter  siter;
 
    slist_foreach(siter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
 
        rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
        if (rw->rw_worker.bgw_notify_pid == pid)
            rw->rw_worker.bgw_notify_pid = 0;
    }
}

References BackgroundWorkerList, BackgroundWorker::bgw_notify_pid, slist_iter::cur, RegisteredBgWorker::rw_worker, slist_container, and slist_foreach.

Referenced by CleanupBackend(), and CleanupBackgroundWorker().

bgworker_die()

static void bgworker_die ( SIGNAL_ARGS  )

static

Definition at line 727 of file bgworker.c.

{
    sigprocmask(SIG_SETMASK, &BlockSig, NULL);
 
    ereport(FATAL,
            (errcode(ERRCODE_ADMIN_SHUTDOWN),
             errmsg("terminating background worker \"%s\" due to administrator command",
                    MyBgworkerEntry->bgw_type)));
}

References BackgroundWorker::bgw_type, BlockSig, ereport, errcode(), errmsg(), FATAL, and MyBgworkerEntry.

Referenced by StartBackgroundWorker().

FindRegisteredWorkerBySlotNumber()

static RegisteredBgWorker* FindRegisteredWorkerBySlotNumber ( int  slotno )

static

Definition at line 220 of file bgworker.c.

{
    slist_iter  siter;
 
    slist_foreach(siter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
 
        rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
        if (rw->rw_shmem_slot == slotno)
            return rw;
    }
 
    return NULL;
}

References BackgroundWorkerList, slist_iter::cur, RegisteredBgWorker::rw_shmem_slot, slist_container, and slist_foreach.

Referenced by BackgroundWorkerStateChange().

ForgetBackgroundWorker()

void ForgetBackgroundWorker

(

slist_mutable_iter *

cur

)

Definition at line 429 of file bgworker.c.

{
    RegisteredBgWorker *rw;
    BackgroundWorkerSlot *slot;
 
    rw = slist_container(RegisteredBgWorker, rw_lnode, cur->cur);
 
    Assert(rw->rw_shmem_slot < max_worker_processes);
    slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
    Assert(slot->in_use);
 
    /*
     * We need a memory barrier here to make sure that the update of
     * parallel_terminate_count completes before the store to in_use.
     */
    if ((rw->rw_worker.bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
        BackgroundWorkerData->parallel_terminate_count++;
 
    pg_memory_barrier();
    slot->in_use = false;
 
    ereport(DEBUG1,
            (errmsg_internal("unregistering background worker \"%s\"",
                             rw->rw_worker.bgw_name)));
 
    slist_delete_current(cur);
    free(rw);
}

References Assert(), BackgroundWorkerData, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_name, BGWORKER_CLASS_PARALLEL, cur, DEBUG1, ereport, errmsg_internal(), free, BackgroundWorkerSlot::in_use, max_worker_processes, BackgroundWorkerArray::parallel_terminate_count, pg_memory_barrier, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, slist_container, slist_delete_current(), and BackgroundWorkerArray::slot.

Referenced by DetermineSleepTime(), ForgetUnstartedBackgroundWorkers(), maybe_start_bgworkers(), ReportBackgroundWorkerExit(), and ResetBackgroundWorkerCrashTimes().

ForgetUnstartedBackgroundWorkers()

void ForgetUnstartedBackgroundWorkers

(

void

)

Definition at line 544 of file bgworker.c.

{
    slist_mutable_iter iter;
 
    slist_foreach_modify(iter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
        BackgroundWorkerSlot *slot;
 
        rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
        Assert(rw->rw_shmem_slot < max_worker_processes);
        slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
 
        /* If it's not yet started, and there's someone waiting ... */
        if (slot->pid == InvalidPid &&
            rw->rw_worker.bgw_notify_pid != 0)
        {
            /* ... then zap it, and notify the waiter */
            int         notify_pid = rw->rw_worker.bgw_notify_pid;
 
            ForgetBackgroundWorker(&iter);
            if (notify_pid != 0)
                kill(notify_pid, SIGUSR1);
        }
    }
}

References Assert(), BackgroundWorkerData, BackgroundWorkerList, BackgroundWorker::bgw_notify_pid, slist_mutable_iter::cur, ForgetBackgroundWorker(), InvalidPid, kill, max_worker_processes, BackgroundWorkerSlot::pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, SIGUSR1, slist_container, slist_foreach_modify, and BackgroundWorkerArray::slot.

Referenced by PostmasterStateMachine().

GetBackgroundWorkerPid()

BgwHandleStatus GetBackgroundWorkerPid	(	BackgroundWorkerHandle *	handle,
		pid_t *	pidp
	)

Definition at line 1071 of file bgworker.c.

{
    BackgroundWorkerSlot *slot;
    pid_t       pid;
 
    Assert(handle->slot < max_worker_processes);
    slot = &BackgroundWorkerData->slot[handle->slot];
 
    /*
     * We could probably arrange to synchronize access to data using memory
     * barriers only, but for now, let's just keep it simple and grab the
     * lock.  It seems unlikely that there will be enough traffic here to
     * result in meaningful contention.
     */
    LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
 
    /*
     * The generation number can't be concurrently changed while we hold the
     * lock.  The pid, which is updated by the postmaster, can change at any
     * time, but we assume such changes are atomic.  So the value we read
     * won't be garbage, but it might be out of date by the time the caller
     * examines it (but that's unavoidable anyway).
     *
     * The in_use flag could be in the process of changing from true to false,
     * but if it is already false then it can't change further.
     */
    if (handle->generation != slot->generation || !slot->in_use)
        pid = 0;
    else
        pid = slot->pid;
 
    /* All done. */
    LWLockRelease(BackgroundWorkerLock);
 
    if (pid == 0)
        return BGWH_STOPPED;
    else if (pid == InvalidPid)
        return BGWH_NOT_YET_STARTED;
    *pidp = pid;
    return BGWH_STARTED;
}

References Assert(), BackgroundWorkerData, BGWH_NOT_YET_STARTED, BGWH_STARTED, BGWH_STOPPED, BackgroundWorkerSlot::generation, BackgroundWorkerHandle::generation, BackgroundWorkerSlot::in_use, InvalidPid, LW_SHARED, LWLockAcquire(), LWLockRelease(), max_worker_processes, BackgroundWorkerSlot::pid, BackgroundWorkerArray::slot, and BackgroundWorkerHandle::slot.

Referenced by check_worker_status(), shm_mq_counterparty_gone(), shm_mq_wait_internal(), WaitForBackgroundWorkerShutdown(), WaitForBackgroundWorkerStartup(), WaitForParallelWorkersToAttach(), WaitForParallelWorkersToFinish(), and WaitForReplicationWorkerAttach().

GetBackgroundWorkerTypeByPid()

const char* GetBackgroundWorkerTypeByPid

(

pid_t

pid

)

Definition at line 1285 of file bgworker.c.

{
    int         slotno;
    bool        found = false;
    static char result[BGW_MAXLEN];
 
    LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
 
    for (slotno = 0; slotno < BackgroundWorkerData->total_slots; slotno++)
    {
        BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
 
        if (slot->pid > 0 && slot->pid == pid)
        {
            strcpy(result, slot->worker.bgw_type);
            found = true;
            break;
        }
    }
 
    LWLockRelease(BackgroundWorkerLock);
 
    if (!found)
        return NULL;
 
    return result;
}

References BackgroundWorkerData, BGW_MAXLEN, BackgroundWorker::bgw_type, LW_SHARED, LWLockAcquire(), LWLockRelease(), BackgroundWorkerSlot::pid, BackgroundWorkerArray::slot, BackgroundWorkerArray::total_slots, and BackgroundWorkerSlot::worker.

Referenced by pg_stat_get_activity().

LookupBackgroundWorkerFunction()

static bgworker_main_type LookupBackgroundWorkerFunction ( const char *  libraryname, const char *  funcname  )

static

Definition at line 1251 of file bgworker.c.

{
    /*
     * If the function is to be loaded from postgres itself, search the
     * InternalBGWorkers array.
     */
    if (strcmp(libraryname, "postgres") == 0)
    {
        int         i;
 
        for (i = 0; i < lengthof(InternalBGWorkers); i++)
        {
            if (strcmp(InternalBGWorkers[i].fn_name, funcname) == 0)
                return InternalBGWorkers[i].fn_addr;
        }
 
        /* We can only reach this by programming error. */
        elog(ERROR, "internal function \"%s\" not found", funcname);
    }
 
    /* Otherwise load from external library. */
    return (bgworker_main_type)
        load_external_function(libraryname, funcname, true, NULL);
}

References elog(), ERROR, fn_addr, fn_name, funcname, i, InternalBGWorkers, lengthof, and load_external_function().

Referenced by StartBackgroundWorker().

RegisterBackgroundWorker()

void RegisterBackgroundWorker

(

BackgroundWorker *

worker

)

Definition at line 875 of file bgworker.c.

{
    RegisteredBgWorker *rw;
    static int  numworkers = 0;
 
    if (!IsUnderPostmaster)
        ereport(DEBUG1,
                (errmsg_internal("registering background worker \"%s\"", worker->bgw_name)));
 
    if (!process_shared_preload_libraries_in_progress &&
        strcmp(worker->bgw_library_name, "postgres") != 0)
    {
        if (!IsUnderPostmaster)
            ereport(LOG,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("background worker \"%s\": must be registered in shared_preload_libraries",
                            worker->bgw_name)));
        return;
    }
 
    if (!SanityCheckBackgroundWorker(worker, LOG))
        return;
 
    if (worker->bgw_notify_pid != 0)
    {
        ereport(LOG,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("background worker \"%s\": only dynamic background workers can request notification",
                        worker->bgw_name)));
        return;
    }
 
    /*
     * Enforce maximum number of workers.  Note this is overly restrictive: we
     * could allow more non-shmem-connected workers, because these don't count
     * towards the MAX_BACKENDS limit elsewhere.  For now, it doesn't seem
     * important to relax this restriction.
     */
    if (++numworkers > max_worker_processes)
    {
        ereport(LOG,
                (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
                 errmsg("too many background workers"),
                 errdetail_plural("Up to %d background worker can be registered with the current settings.",
                                  "Up to %d background workers can be registered with the current settings.",
                                  max_worker_processes,
                                  max_worker_processes),
                 errhint("Consider increasing the configuration parameter \"max_worker_processes\".")));
        return;
    }
 
    /*
     * Copy the registration data into the registered workers list.
     */
    rw = malloc(sizeof(RegisteredBgWorker));
    if (rw == NULL)
    {
        ereport(LOG,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
        return;
    }
 
    rw->rw_worker = *worker;
    rw->rw_backend = NULL;
    rw->rw_pid = 0;
    rw->rw_child_slot = 0;
    rw->rw_crashed_at = 0;
    rw->rw_terminate = false;
 
    slist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
}

References BackgroundWorkerList, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_name, BackgroundWorker::bgw_notify_pid, DEBUG1, ereport, errcode(), errdetail_plural(), errhint(), errmsg(), errmsg_internal(), IsUnderPostmaster, LOG, malloc, max_worker_processes, process_shared_preload_libraries_in_progress, RegisteredBgWorker::rw_backend, RegisteredBgWorker::rw_child_slot, RegisteredBgWorker::rw_crashed_at, RegisteredBgWorker::rw_lnode, RegisteredBgWorker::rw_pid, RegisteredBgWorker::rw_terminate, RegisteredBgWorker::rw_worker, SanityCheckBackgroundWorker(), and slist_push_head().

Referenced by _PG_init(), ApplyLauncherRegister(), and apw_start_leader_worker().

RegisterDynamicBackgroundWorker()

bool RegisterDynamicBackgroundWorker	(	BackgroundWorker *	worker,
		BackgroundWorkerHandle **	handle
	)

Definition at line 959 of file bgworker.c.

{
    int         slotno;
    bool        success = false;
    bool        parallel;
    uint64      generation = 0;
 
    /*
     * We can't register dynamic background workers from the postmaster. If
     * this is a standalone backend, we're the only process and can't start
     * any more.  In a multi-process environment, it might be theoretically
     * possible, but we don't currently support it due to locking
     * considerations; see comments on the BackgroundWorkerSlot data
     * structure.
     */
    if (!IsUnderPostmaster)
        return false;
 
    if (!SanityCheckBackgroundWorker(worker, ERROR))
        return false;
 
    parallel = (worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0;
 
    LWLockAcquire(BackgroundWorkerLock, LW_EXCLUSIVE);
 
    /*
     * If this is a parallel worker, check whether there are already too many
     * parallel workers; if so, don't register another one.  Our view of
     * parallel_terminate_count may be slightly stale, but that doesn't really
     * matter: we would have gotten the same result if we'd arrived here
     * slightly earlier anyway.  There's no help for it, either, since the
     * postmaster must not take locks; a memory barrier wouldn't guarantee
     * anything useful.
     */
    if (parallel && (BackgroundWorkerData->parallel_register_count -
                     BackgroundWorkerData->parallel_terminate_count) >=
        max_parallel_workers)
    {
        Assert(BackgroundWorkerData->parallel_register_count -
               BackgroundWorkerData->parallel_terminate_count <=
               MAX_PARALLEL_WORKER_LIMIT);
        LWLockRelease(BackgroundWorkerLock);
        return false;
    }
 
    /*
     * Look for an unused slot.  If we find one, grab it.
     */
    for (slotno = 0; slotno < BackgroundWorkerData->total_slots; ++slotno)
    {
        BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
 
        if (!slot->in_use)
        {
            memcpy(&slot->worker, worker, sizeof(BackgroundWorker));
            slot->pid = InvalidPid; /* indicates not started yet */
            slot->generation++;
            slot->terminate = false;
            generation = slot->generation;
            if (parallel)
                BackgroundWorkerData->parallel_register_count++;
 
            /*
             * Make sure postmaster doesn't see the slot as in use before it
             * sees the new contents.
             */
            pg_write_barrier();
 
            slot->in_use = true;
            success = true;
            break;
        }
    }
 
    LWLockRelease(BackgroundWorkerLock);
 
    /* If we found a slot, tell the postmaster to notice the change. */
    if (success)
        SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
 
    /*
     * If we found a slot and the user has provided a handle, initialize it.
     */
    if (success && handle)
    {
        *handle = palloc(sizeof(BackgroundWorkerHandle));
        (*handle)->slot = slotno;
        (*handle)->generation = generation;
    }
 
    return success;
}

References Assert(), BackgroundWorkerData, BackgroundWorker::bgw_flags, BGWORKER_CLASS_PARALLEL, ERROR, BackgroundWorkerSlot::generation, BackgroundWorkerSlot::in_use, InvalidPid, IsUnderPostmaster, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MAX_PARALLEL_WORKER_LIMIT, max_parallel_workers, palloc(), BackgroundWorkerArray::parallel_register_count, BackgroundWorkerArray::parallel_terminate_count, pg_write_barrier, BackgroundWorkerSlot::pid, PMSIGNAL_BACKGROUND_WORKER_CHANGE, SanityCheckBackgroundWorker(), SendPostmasterSignal(), BackgroundWorkerArray::slot, success, BackgroundWorkerSlot::terminate, BackgroundWorkerArray::total_slots, and BackgroundWorkerSlot::worker.

Referenced by apw_start_database_worker(), apw_start_leader_worker(), LaunchParallelWorkers(), logicalrep_worker_launch(), setup_background_workers(), and worker_spi_launch().

ReportBackgroundWorkerExit()

void ReportBackgroundWorkerExit

(

slist_mutable_iter *

cur

)

Definition at line 483 of file bgworker.c.

{
    RegisteredBgWorker *rw;
    BackgroundWorkerSlot *slot;
    int         notify_pid;
 
    rw = slist_container(RegisteredBgWorker, rw_lnode, cur->cur);
 
    Assert(rw->rw_shmem_slot < max_worker_processes);
    slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
    slot->pid = rw->rw_pid;
    notify_pid = rw->rw_worker.bgw_notify_pid;
 
    /*
     * If this worker is slated for deregistration, do that before notifying
     * the process which started it.  Otherwise, if that process tries to
     * reuse the slot immediately, it might not be available yet.  In theory
     * that could happen anyway if the process checks slot->pid at just the
     * wrong moment, but this makes the window narrower.
     */
    if (rw->rw_terminate ||
        rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
        ForgetBackgroundWorker(cur);
 
    if (notify_pid != 0)
        kill(notify_pid, SIGUSR1);
}

References Assert(), BackgroundWorkerData, BGW_NEVER_RESTART, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, cur, ForgetBackgroundWorker(), kill, max_worker_processes, BackgroundWorkerSlot::pid, RegisteredBgWorker::rw_pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_terminate, RegisteredBgWorker::rw_worker, SIGUSR1, slist_container, and BackgroundWorkerArray::slot.

Referenced by CleanupBackgroundWorker().

ReportBackgroundWorkerPID()

void ReportBackgroundWorkerPID

(

RegisteredBgWorker *

rw

)

Definition at line 464 of file bgworker.c.

{
    BackgroundWorkerSlot *slot;
 
    Assert(rw->rw_shmem_slot < max_worker_processes);
    slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
    slot->pid = rw->rw_pid;
 
    if (rw->rw_worker.bgw_notify_pid != 0)
        kill(rw->rw_worker.bgw_notify_pid, SIGUSR1);
}

References Assert(), BackgroundWorkerData, BackgroundWorker::bgw_notify_pid, kill, max_worker_processes, BackgroundWorkerSlot::pid, RegisteredBgWorker::rw_pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, SIGUSR1, and BackgroundWorkerArray::slot.

Referenced by BackgroundWorkerStateChange(), and do_start_bgworker().

ResetBackgroundWorkerCrashTimes()

void ResetBackgroundWorkerCrashTimes

(

void

)

Definition at line 582 of file bgworker.c.

{
    slist_mutable_iter iter;
 
    slist_foreach_modify(iter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
 
        rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
 
        if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
        {
            /*
             * Workers marked BGW_NEVER_RESTART shouldn't get relaunched after
             * the crash, so forget about them.  (If we wait until after the
             * crash to forget about them, and they are parallel workers,
             * parallel_terminate_count will get incremented after we've
             * already zeroed parallel_register_count, which would be bad.)
             */
            ForgetBackgroundWorker(&iter);
        }
        else
        {
            /*
             * The accounting which we do via parallel_register_count and
             * parallel_terminate_count would get messed up if a worker marked
             * parallel could survive a crash and restart cycle. All such
             * workers should be marked BGW_NEVER_RESTART, and thus control
             * should never reach this branch.
             */
            Assert((rw->rw_worker.bgw_flags & BGWORKER_CLASS_PARALLEL) == 0);
 
            /*
             * Allow this worker to be restarted immediately after we finish
             * resetting.
             */
            rw->rw_crashed_at = 0;
 
            /*
             * If there was anyone waiting for it, they're history.
             */
            rw->rw_worker.bgw_notify_pid = 0;
        }
    }
}

References Assert(), BackgroundWorkerList, BackgroundWorker::bgw_flags, BGW_NEVER_RESTART, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BGWORKER_CLASS_PARALLEL, slist_mutable_iter::cur, ForgetBackgroundWorker(), RegisteredBgWorker::rw_crashed_at, RegisteredBgWorker::rw_worker, slist_container, and slist_foreach_modify.

Referenced by PostmasterStateMachine().

SanityCheckBackgroundWorker()

static bool SanityCheckBackgroundWorker ( BackgroundWorker *  worker, int  elevel  )

static

Definition at line 655 of file bgworker.c.

{
    /* sanity check for flags */
 
    /*
     * We used to support workers not connected to shared memory, but don't
     * anymore. Thus this is a required flag now. We're not removing the flag
     * for compatibility reasons and because the flag still provides some
     * signal when reading code.
     */
    if (!(worker->bgw_flags & BGWORKER_SHMEM_ACCESS))
    {
        ereport(elevel,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("background worker \"%s\": background workers without shared memory access are not supported",
                        worker->bgw_name)));
        return false;
    }
 
    if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
    {
        if (worker->bgw_start_time == BgWorkerStart_PostmasterStart)
        {
            ereport(elevel,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("background worker \"%s\": cannot request database access if starting at postmaster start",
                            worker->bgw_name)));
            return false;
        }
 
        /* XXX other checks? */
    }
 
    if ((worker->bgw_restart_time < 0 &&
         worker->bgw_restart_time != BGW_NEVER_RESTART) ||
        (worker->bgw_restart_time > USECS_PER_DAY / 1000))
    {
        ereport(elevel,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("background worker \"%s\": invalid restart interval",
                        worker->bgw_name)));
        return false;
    }
 
    /*
     * Parallel workers may not be configured for restart, because the
     * parallel_register_count/parallel_terminate_count accounting can't
     * handle parallel workers lasting through a crash-and-restart cycle.
     */
    if (worker->bgw_restart_time != BGW_NEVER_RESTART &&
        (worker->bgw_flags & BGWORKER_CLASS_PARALLEL) != 0)
    {
        ereport(elevel,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("background worker \"%s\": parallel workers may not be configured for restart",
                        worker->bgw_name)));
        return false;
    }
 
    /*
     * If bgw_type is not filled in, use bgw_name.
     */
    if (strcmp(worker->bgw_type, "") == 0)
        strcpy(worker->bgw_type, worker->bgw_name);
 
    return true;
}

References BackgroundWorker::bgw_flags, BackgroundWorker::bgw_name, BGW_NEVER_RESTART, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, BGWORKER_BACKEND_DATABASE_CONNECTION, BGWORKER_CLASS_PARALLEL, BGWORKER_SHMEM_ACCESS, BgWorkerStart_PostmasterStart, ereport, errcode(), errmsg(), and USECS_PER_DAY.

Referenced by RegisterBackgroundWorker(), and RegisterDynamicBackgroundWorker().

StartBackgroundWorker()

void StartBackgroundWorker

(

void

)

Definition at line 744 of file bgworker.c.

{
    sigjmp_buf  local_sigjmp_buf;
    BackgroundWorker *worker = MyBgworkerEntry;
    bgworker_main_type entrypt;
 
    if (worker == NULL)
        elog(FATAL, "unable to find bgworker entry");
 
    IsBackgroundWorker = true;
 
    MyBackendType = B_BG_WORKER;
    init_ps_display(worker->bgw_name);
 
    SetProcessingMode(InitProcessing);
 
    /* Apply PostAuthDelay */
    if (PostAuthDelay > 0)
        pg_usleep(PostAuthDelay * 1000000L);
 
    /*
     * Set up signal handlers.
     */
    if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
    {
        /*
         * SIGINT is used to signal canceling the current action
         */
        pqsignal(SIGINT, StatementCancelHandler);
        pqsignal(SIGUSR1, procsignal_sigusr1_handler);
        pqsignal(SIGFPE, FloatExceptionHandler);
 
        /* XXX Any other handlers needed here? */
    }
    else
    {
        pqsignal(SIGINT, SIG_IGN);
        pqsignal(SIGUSR1, SIG_IGN);
        pqsignal(SIGFPE, SIG_IGN);
    }
    pqsignal(SIGTERM, bgworker_die);
    /* SIGQUIT handler was already set up by InitPostmasterChild */
    pqsignal(SIGHUP, SIG_IGN);
 
    InitializeTimeouts();       /* establishes SIGALRM handler */
 
    pqsignal(SIGPIPE, SIG_IGN);
    pqsignal(SIGUSR2, SIG_IGN);
    pqsignal(SIGCHLD, SIG_DFL);
 
    /*
     * If an exception is encountered, processing resumes here.
     *
     * We just need to clean up, report the error, and go away.
     */
    if (sigsetjmp(local_sigjmp_buf, 1) != 0)
    {
        /* Since not using PG_TRY, must reset error stack by hand */
        error_context_stack = NULL;
 
        /* Prevent interrupts while cleaning up */
        HOLD_INTERRUPTS();
 
        /*
         * sigsetjmp will have blocked all signals, but we may need to accept
         * signals while communicating with our parallel leader.  Once we've
         * done HOLD_INTERRUPTS() it should be safe to unblock signals.
         */
        BackgroundWorkerUnblockSignals();
 
        /* Report the error to the parallel leader and the server log */
        EmitErrorReport();
 
        /*
         * Do we need more cleanup here?  For shmem-connected bgworkers, we
         * will call InitProcess below, which will install ProcKill as exit
         * callback.  That will take care of releasing locks, etc.
         */
 
        /* and go away */
        proc_exit(1);
    }
 
    /* We can now handle ereport(ERROR) */
    PG_exception_stack = &local_sigjmp_buf;
 
    /*
     * Create a per-backend PGPROC struct in shared memory, except in the
     * EXEC_BACKEND case where this was done in SubPostmasterMain. We must do
     * this before we can use LWLocks (and in the EXEC_BACKEND case we already
     * had to do some stuff with LWLocks).
     */
#ifndef EXEC_BACKEND
    InitProcess();
#endif
 
    /*
     * Early initialization.
     */
    BaseInit();
 
    /*
     * Look up the entry point function, loading its library if necessary.
     */
    entrypt = LookupBackgroundWorkerFunction(worker->bgw_library_name,
                                             worker->bgw_function_name);
 
    /*
     * Note that in normal processes, we would call InitPostgres here.  For a
     * worker, however, we don't know what database to connect to, yet; so we
     * need to wait until the user code does it via
     * BackgroundWorkerInitializeConnection().
     */
 
    /*
     * Now invoke the user-defined worker code
     */
    entrypt(worker->bgw_main_arg);
 
    /* ... and if it returns, we're done */
    proc_exit(0);
}

References B_BG_WORKER, BackgroundWorkerUnblockSignals(), BaseInit(), BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BackgroundWorker::bgw_name, BGWORKER_BACKEND_DATABASE_CONNECTION, bgworker_die(), elog(), EmitErrorReport(), error_context_stack, FATAL, FloatExceptionHandler(), HOLD_INTERRUPTS, init_ps_display(), InitializeTimeouts(), InitProcess(), InitProcessing, IsBackgroundWorker, LookupBackgroundWorkerFunction(), MyBackendType, MyBgworkerEntry, PG_exception_stack, pg_usleep(), PostAuthDelay, pqsignal(), proc_exit(), procsignal_sigusr1_handler(), SetProcessingMode, SIG_DFL, SIG_IGN, SIGCHLD, SIGHUP, SIGPIPE, SIGUSR1, SIGUSR2, and StatementCancelHandler().

Referenced by do_start_bgworker().

TerminateBackgroundWorker()

void TerminateBackgroundWorker

(

BackgroundWorkerHandle *

handle

)

Definition at line 1210 of file bgworker.c.

{
    BackgroundWorkerSlot *slot;
    bool        signal_postmaster = false;
 
    Assert(handle->slot < max_worker_processes);
    slot = &BackgroundWorkerData->slot[handle->slot];
 
    /* Set terminate flag in shared memory, unless slot has been reused. */
    LWLockAcquire(BackgroundWorkerLock, LW_EXCLUSIVE);
    if (handle->generation == slot->generation)
    {
        slot->terminate = true;
        signal_postmaster = true;
    }
    LWLockRelease(BackgroundWorkerLock);
 
    /* Make sure the postmaster notices the change to shared memory. */
    if (signal_postmaster)
        SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
}

References Assert(), BackgroundWorkerData, BackgroundWorkerSlot::generation, BackgroundWorkerHandle::generation, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), max_worker_processes, PMSIGNAL_BACKGROUND_WORKER_CHANGE, SendPostmasterSignal(), BackgroundWorkerArray::slot, BackgroundWorkerHandle::slot, and BackgroundWorkerSlot::terminate.

Referenced by cleanup_background_workers(), and DestroyParallelContext().

WaitForBackgroundWorkerShutdown()

BgwHandleStatus WaitForBackgroundWorkerShutdown

(

BackgroundWorkerHandle *

handle

)

Definition at line 1171 of file bgworker.c.

{
    BgwHandleStatus status;
    int         rc;
 
    for (;;)
    {
        pid_t       pid;
 
        CHECK_FOR_INTERRUPTS();
 
        status = GetBackgroundWorkerPid(handle, &pid);
        if (status == BGWH_STOPPED)
            break;
 
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_POSTMASTER_DEATH, 0,
                       WAIT_EVENT_BGWORKER_SHUTDOWN);
 
        if (rc & WL_POSTMASTER_DEATH)
        {
            status = BGWH_POSTMASTER_DIED;
            break;
        }
 
        ResetLatch(MyLatch);
    }
 
    return status;
}

References BGWH_POSTMASTER_DIED, BGWH_STOPPED, CHECK_FOR_INTERRUPTS, GetBackgroundWorkerPid(), MyLatch, ResetLatch(), status(), WAIT_EVENT_BGWORKER_SHUTDOWN, WaitLatch(), WL_LATCH_SET, and WL_POSTMASTER_DEATH.

Referenced by apw_start_database_worker(), and WaitForParallelWorkersToExit().

WaitForBackgroundWorkerStartup()

BgwHandleStatus WaitForBackgroundWorkerStartup	(	BackgroundWorkerHandle *	handle,
		pid_t *	pidp
	)

Definition at line 1126 of file bgworker.c.

{
    BgwHandleStatus status;
    int         rc;
 
    for (;;)
    {
        pid_t       pid;
 
        CHECK_FOR_INTERRUPTS();
 
        status = GetBackgroundWorkerPid(handle, &pid);
        if (status == BGWH_STARTED)
            *pidp = pid;
        if (status != BGWH_NOT_YET_STARTED)
            break;
 
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_POSTMASTER_DEATH, 0,
                       WAIT_EVENT_BGWORKER_STARTUP);
 
        if (rc & WL_POSTMASTER_DEATH)
        {
            status = BGWH_POSTMASTER_DIED;
            break;
        }
 
        ResetLatch(MyLatch);
    }
 
    return status;
}

References BGWH_NOT_YET_STARTED, BGWH_POSTMASTER_DIED, BGWH_STARTED, CHECK_FOR_INTERRUPTS, GetBackgroundWorkerPid(), MyLatch, ResetLatch(), status(), WAIT_EVENT_BGWORKER_STARTUP, WaitLatch(), WL_LATCH_SET, and WL_POSTMASTER_DEATH.

Referenced by apw_start_leader_worker(), and worker_spi_launch().

Variable Documentation

BackgroundWorkerData

BackgroundWorkerArray* BackgroundWorkerData

static

Definition at line 110 of file bgworker.c.

Referenced by BackgroundWorkerShmemInit(), BackgroundWorkerStateChange(), ForgetBackgroundWorker(), ForgetUnstartedBackgroundWorkers(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), RegisterDynamicBackgroundWorker(), ReportBackgroundWorkerExit(), ReportBackgroundWorkerPID(), and TerminateBackgroundWorker().

BackgroundWorkerList

slist_head BackgroundWorkerList = SLIST_STATIC_INIT(BackgroundWorkerList)

Definition at line 42 of file bgworker.c.

Referenced by BackgroundWorkerShmemInit(), BackgroundWorkerStateChange(), BackgroundWorkerStopNotifications(), CleanupBackgroundWorker(), DetermineSleepTime(), FindRegisteredWorkerBySlotNumber(), ForgetUnstartedBackgroundWorkers(), HandleChildCrash(), maybe_start_bgworkers(), RegisterBackgroundWorker(), and ResetBackgroundWorkerCrashTimes().

fn_addr

bgworker_main_type fn_addr

Definition at line 119 of file bgworker.c.

Referenced by LookupBackgroundWorkerFunction().

fn_name

const char* fn_name

Definition at line 118 of file bgworker.c.

Referenced by LookupBackgroundWorkerFunction().

const { ... } InternalBGWorkers[]

Initial value:

=
 
{
    {
        "ParallelWorkerMain", ParallelWorkerMain
    },
    {
        "ApplyLauncherMain", ApplyLauncherMain
    },
    {
        "ApplyWorkerMain", ApplyWorkerMain
    },
    {
        "ParallelApplyWorkerMain", ParallelApplyWorkerMain
    }
}

Referenced by LookupBackgroundWorkerFunction().