#include "datatype/timestamp.h"
#include "lib/ilist.h"
#include "postmaster/bgworker.h"

Include dependency graph for bgworker_internals.h:

This graph shows which files directly or indirectly include this file:

Data Structures
struct	RegisteredBgWorker

Macros
#define	MAX_PARALLEL_WORKER_LIMIT 1024

Typedefs
typedef struct RegisteredBgWorker	RegisteredBgWorker

Variables
PGDLLIMPORT dlist_head	BackgroundWorkerList

Macro Definition Documentation

◆ MAX_PARALLEL_WORKER_LIMIT

#define MAX_PARALLEL_WORKER_LIMIT 1024

Definition at line 24 of file bgworker_internals.h.

Typedef Documentation

◆ RegisteredBgWorker

typedef struct RegisteredBgWorker RegisteredBgWorker

Function Documentation

◆ BackgroundWorkerMain()

pg_noreturn void BackgroundWorkerMain	(	const void *	startup_data,
		size_t	startup_data_len
	)

extern

Definition at line 741 of file bgworker.c.

{
    sigjmp_buf  local_sigjmp_buf;
    BackgroundWorker *worker;
    bgworker_main_type entrypt;
 
    if (startup_data == NULL)
        elog(FATAL, "unable to find bgworker entry");
    Assert(startup_data_len == sizeof(BackgroundWorker));
    worker = MemoryContextAlloc(TopMemoryContext, sizeof(BackgroundWorker));
    memcpy(worker, startup_data, sizeof(BackgroundWorker));
 
    /*
     * Now that we're done reading the startup data, release postmaster's
     * working memory context.
     */
    if (PostmasterContext)
    {
        MemoryContextDelete(PostmasterContext);
        PostmasterContext = NULL;
    }
 
    MyBgworkerEntry = worker;
    init_ps_display(worker->bgw_name);
 
    Assert(GetProcessingMode() == 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, PG_SIG_IGN);
        pqsignal(SIGUSR1, PG_SIG_IGN);
        pqsignal(SIGFPE, PG_SIG_IGN);
    }
    pqsignal(SIGTERM, die);
    /* SIGQUIT handler was already set up by InitPostmasterChild */
    pqsignal(SIGHUP, PG_SIG_IGN);
 
    InitializeTimeouts();       /* establishes SIGALRM handler */
 
    pqsignal(SIGPIPE, PG_SIG_IGN);
    pqsignal(SIGUSR2, PG_SIG_IGN);
    pqsignal(SIGCHLD, PG_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.  We must do this
     * before we can use LWLocks or access any shared memory.
     */
    InitProcess();
 
    /*
     * 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 Assert, BackgroundWorkerUnblockSignals(), BaseInit(), BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BackgroundWorker::bgw_name, BGWORKER_BACKEND_DATABASE_CONNECTION, die, elog, EmitErrorReport(), error_context_stack, FATAL, fb(), FloatExceptionHandler(), GetProcessingMode, HOLD_INTERRUPTS, init_ps_display(), InitializeTimeouts(), InitProcess(), InitProcessing, LookupBackgroundWorkerFunction(), memcpy(), MemoryContextAlloc(), MemoryContextDelete(), MyBgworkerEntry, PG_exception_stack, PG_SIG_DFL, PG_SIG_IGN, pg_usleep(), PostAuthDelay, PostmasterContext, pqsignal, proc_exit(), procsignal_sigusr1_handler(), SIGCHLD, SIGHUP, SIGPIPE, SIGUSR1, SIGUSR2, StatementCancelHandler(), and TopMemoryContext.

◆ BackgroundWorkerStateChange()

void BackgroundWorkerStateChange ( bool allow_new_workers )

extern

Definition at line 272 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 = MemoryContextAllocExtended(PostmasterContext,
                                        sizeof(RegisteredBgWorker),
                                        MCXT_ALLOC_NO_OOM | MCXT_ALLOC_ZERO);
        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, MAXPGPATH);
        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_pid = 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)));
 
        dlist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
    }
}

Referenced by process_pm_pmsignal().

◆ BackgroundWorkerStopNotifications()

void BackgroundWorkerStopNotifications ( pid_t pid )

extern

Definition at line 540 of file bgworker.c.

{
    dlist_iter  iter;
 
    dlist_foreach(iter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
 
        rw = dlist_container(RegisteredBgWorker, rw_lnode, iter.cur);
        if (rw->rw_worker.bgw_notify_pid == pid)
            rw->rw_worker.bgw_notify_pid = 0;
    }
}

References BackgroundWorkerList, BackgroundWorker::bgw_notify_pid, dlist_iter::cur, dlist_container, dlist_foreach, and RegisteredBgWorker::rw_worker.

Referenced by CleanupBackend().

◆ ForgetBackgroundWorker()

void ForgetBackgroundWorker ( RegisteredBgWorker * rw )

extern

Definition at line 455 of file bgworker.c.

{
    BackgroundWorkerSlot *slot;
 
    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)));
 
    dlist_delete(&rw->rw_lnode);
    pfree(rw);
}

References Assert, BackgroundWorkerData, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_name, BGWORKER_CLASS_PARALLEL, DEBUG1, dlist_delete(), ereport, errmsg_internal(), BackgroundWorkerSlot::in_use, max_worker_processes, BackgroundWorkerArray::parallel_terminate_count, pfree(), pg_memory_barrier, RegisteredBgWorker::rw_lnode, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, and BackgroundWorkerArray::slot.

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

◆ ForgetUnstartedBackgroundWorkers()

void ForgetUnstartedBackgroundWorkers ( void )

extern

Definition at line 567 of file bgworker.c.

{
    dlist_mutable_iter iter;
 
    dlist_foreach_modify(iter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
        BackgroundWorkerSlot *slot;
 
        rw = dlist_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(rw);
            if (notify_pid != 0)
                kill(notify_pid, SIGUSR1);
        }
    }
}

References Assert, BackgroundWorkerData, BackgroundWorkerList, BackgroundWorker::bgw_notify_pid, dlist_mutable_iter::cur, dlist_container, dlist_foreach_modify, fb(), ForgetBackgroundWorker(), InvalidPid, kill, max_worker_processes, BackgroundWorkerSlot::pid, RegisteredBgWorker::rw_shmem_slot, RegisteredBgWorker::rw_worker, SIGUSR1, and BackgroundWorkerArray::slot.

Referenced by PostmasterStateMachine().

◆ ReportBackgroundWorkerExit()

void ReportBackgroundWorkerExit ( RegisteredBgWorker * rw )

extern

Definition at line 509 of file bgworker.c.

{
    BackgroundWorkerSlot *slot;
    int         notify_pid;
 
    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(rw);
 
    if (notify_pid != 0)
        kill(notify_pid, SIGUSR1);
}

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

Referenced by CleanupBackend().

◆ ReportBackgroundWorkerPID()

void ReportBackgroundWorkerPID ( RegisteredBgWorker * rw )

extern

Definition at line 487 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 StartBackgroundWorker().

◆ ResetBackgroundWorkerCrashTimes()

void ResetBackgroundWorkerCrashTimes ( void )

extern

Definition at line 605 of file bgworker.c.

{
    dlist_mutable_iter iter;
 
    dlist_foreach_modify(iter, &BackgroundWorkerList)
    {
        RegisteredBgWorker *rw;
 
        rw = dlist_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(rw);
        }
        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;
            rw->rw_pid = 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, dlist_mutable_iter::cur, dlist_container, dlist_foreach_modify, ForgetBackgroundWorker(), RegisteredBgWorker::rw_crashed_at, RegisteredBgWorker::rw_pid, and RegisteredBgWorker::rw_worker.

Referenced by PostmasterStateMachine().

Variable Documentation

◆ BackgroundWorkerList

PGDLLIMPORT dlist_head BackgroundWorkerList

extern

Definition at line 45 of file bgworker.c.

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

Functions
void	BackgroundWorkerStateChange (bool allow_new_workers)

void	ForgetBackgroundWorker (RegisteredBgWorker *rw)

void	ReportBackgroundWorkerPID (RegisteredBgWorker *rw)

void	ReportBackgroundWorkerExit (RegisteredBgWorker *rw)

void	BackgroundWorkerStopNotifications (pid_t pid)

void	ForgetUnstartedBackgroundWorkers (void)

void	ResetBackgroundWorkerCrashTimes (void)

pg_noreturn void	BackgroundWorkerMain (const void *startup_data, size_t startup_data_len)

Data Structures

Macros

Typedefs

Functions

Variables

Macro Definition Documentation

◆ MAX_PARALLEL_WORKER_LIMIT

Typedef Documentation

◆ RegisteredBgWorker

Function Documentation

◆ BackgroundWorkerMain()

◆ BackgroundWorkerStateChange()

◆ BackgroundWorkerStopNotifications()

◆ ForgetBackgroundWorker()

◆ ForgetUnstartedBackgroundWorkers()

◆ ReportBackgroundWorkerExit()

◆ ReportBackgroundWorkerPID()

◆ ResetBackgroundWorkerCrashTimes()

Variable Documentation

◆ BackgroundWorkerList