#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include <sys/stat.h>
#include "miscadmin.h"
#include "storage/dsm.h"
#include "storage/ipc.h"
#include "tcop/tcopprot.h"

Include dependency graph for ipc.c:

Go to the source code of this file.

Data Structures
struct	ONEXIT

Macros
#define	MAX_ON_EXITS 20

Functions
static void	proc_exit_prepare (int code)

void	proc_exit (int code)

void	shmem_exit (int code)

static void	atexit_callback (void)

void	on_proc_exit (pg_on_exit_callback function, Datum arg)

void	before_shmem_exit (pg_on_exit_callback function, Datum arg)

void	on_shmem_exit (pg_on_exit_callback function, Datum arg)

void	cancel_before_shmem_exit (pg_on_exit_callback function, Datum arg)

void	on_exit_reset (void)

void	check_on_shmem_exit_lists_are_empty (void)

Variables
bool	proc_exit_inprogress = false

bool	shmem_exit_inprogress = false

static bool	atexit_callback_setup = false

static struct ONEXIT	on_proc_exit_list [MAX_ON_EXITS]

static struct ONEXIT	on_shmem_exit_list [MAX_ON_EXITS]

static struct ONEXIT	before_shmem_exit_list [MAX_ON_EXITS]

static int	on_proc_exit_index

static int	on_shmem_exit_index

static int	before_shmem_exit_index

Macro Definition Documentation

◆ MAX_ON_EXITS

#define MAX_ON_EXITS 20

Definition at line 71 of file ipc.c.

Function Documentation

◆ atexit_callback()

static void atexit_callback ( void )

static

Definition at line 294 of file ipc.c.

{
    /* Clean up everything that must be cleaned up */
    /* ... too bad we don't know the real exit code ... */
    proc_exit_prepare(-1);
}

References proc_exit_prepare().

Referenced by before_shmem_exit(), on_proc_exit(), and on_shmem_exit().

◆ before_shmem_exit()

void before_shmem_exit	(	pg_on_exit_callback	function,
		Datum	arg
	)

Definition at line 337 of file ipc.c.

{
    if (before_shmem_exit_index >= MAX_ON_EXITS)
        ereport(FATAL,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg_internal("out of before_shmem_exit slots")));
 
    before_shmem_exit_list[before_shmem_exit_index].function = function;
    before_shmem_exit_list[before_shmem_exit_index].arg = arg;
 
    ++before_shmem_exit_index;
 
    if (!atexit_callback_setup)
    {
        atexit(atexit_callback);
        atexit_callback_setup = true;
    }
}

References ONEXIT::arg, arg, atexit_callback(), atexit_callback_setup, before_shmem_exit_index, before_shmem_exit_list, ereport, errcode(), errmsg_internal(), FATAL, ONEXIT::function, function, and MAX_ON_EXITS.

Referenced by ApplyLauncherMain(), AtEOXact_Namespace(), autoprewarm_main(), AuxiliaryProcessMainCommon(), CheckpointerMain(), Exec_ListenPreCommit(), InitPostgres(), InitTemporaryFileAccess(), injection_points_set_local(), LoadArchiveLibrary(), LockGXact(), logicalrep_worker_attach(), MarkAsPreparing(), ParallelApplyWorkerMain(), ParallelWorkerMain(), pgstat_initialize(), register_persistent_abort_backup_handler(), ReplicationSlotInitialize(), ReplSlotSyncWorkerMain(), and SetupApplyOrSyncWorker().

◆ cancel_before_shmem_exit()

void cancel_before_shmem_exit	(	pg_on_exit_callback	function,
		Datum	arg
	)

Definition at line 394 of file ipc.c.

{
    if (before_shmem_exit_index > 0 &&
        before_shmem_exit_list[before_shmem_exit_index - 1].function
        == function &&
        before_shmem_exit_list[before_shmem_exit_index - 1].arg == arg)
        --before_shmem_exit_index;
    else
        elog(ERROR, "before_shmem_exit callback (%p,0x%llx) is not the latest entry",
             function, (long long) arg);
}

References arg, before_shmem_exit_index, before_shmem_exit_list, elog, ERROR, and function.

◆ check_on_shmem_exit_lists_are_empty()

void check_on_shmem_exit_lists_are_empty ( void )

Definition at line 432 of file ipc.c.

{
    if (before_shmem_exit_index)
        elog(FATAL, "before_shmem_exit has been called prematurely");
    if (on_shmem_exit_index)
        elog(FATAL, "on_shmem_exit has been called prematurely");
    /* Checking DSM detach state seems unnecessary given the above */
}

References before_shmem_exit_index, elog, FATAL, and on_shmem_exit_index.

Referenced by BackendInitialize().

◆ on_exit_reset()

void on_exit_reset ( void )

Definition at line 416 of file ipc.c.

{
    before_shmem_exit_index = 0;
    on_shmem_exit_index = 0;
    on_proc_exit_index = 0;
    reset_on_dsm_detach();
}

References before_shmem_exit_index, on_proc_exit_index, on_shmem_exit_index, and reset_on_dsm_detach().

Referenced by InitPostmasterChild().

◆ on_proc_exit()

void on_proc_exit	(	pg_on_exit_callback	function,
		Datum	arg
	)

Definition at line 309 of file ipc.c.

{
    if (on_proc_exit_index >= MAX_ON_EXITS)
        ereport(FATAL,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg_internal("out of on_proc_exit slots")));
 
    on_proc_exit_list[on_proc_exit_index].function = function;
    on_proc_exit_list[on_proc_exit_index].arg = arg;
 
    ++on_proc_exit_index;
 
    if (!atexit_callback_setup)
    {
        atexit(atexit_callback);
        atexit_callback_setup = true;
    }
}

References ONEXIT::arg, arg, atexit_callback(), atexit_callback_setup, ereport, errcode(), errmsg_internal(), FATAL, ONEXIT::function, function, MAX_ON_EXITS, on_proc_exit_index, and on_proc_exit_list.

Referenced by CreateLockFile(), InitCatCache(), llvm_session_initialize(), PostgresMain(), PostmasterMain(), pq_init(), select_perl_context(), sepgsql_avc_init(), and smgrinit().

◆ on_shmem_exit()

void on_shmem_exit	(	pg_on_exit_callback	function,
		Datum	arg
	)

Definition at line 365 of file ipc.c.

{
    if (on_shmem_exit_index >= MAX_ON_EXITS)
        ereport(FATAL,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg_internal("out of on_shmem_exit slots")));
 
    on_shmem_exit_list[on_shmem_exit_index].function = function;
    on_shmem_exit_list[on_shmem_exit_index].arg = arg;
 
    ++on_shmem_exit_index;
 
    if (!atexit_callback_setup)
    {
        atexit(atexit_callback);
        atexit_callback_setup = true;
    }
}

References ONEXIT::arg, arg, atexit_callback(), atexit_callback_setup, ereport, errcode(), errmsg_internal(), FATAL, ONEXIT::function, function, MAX_ON_EXITS, on_shmem_exit_index, and on_shmem_exit_list.

Referenced by AutoVacWorkerMain(), CreateAuxProcessResourceOwner(), dsm_postmaster_startup(), InitAuxiliaryProcess(), InitBufferManagerAccess(), InitProcess(), InitProcessPhase2(), InitWalSenderSlot(), InternalIpcMemoryCreate(), PgArchiverMain(), PGReserveSemaphores(), PGSharedMemoryCreate(), pgss_shmem_startup(), pgstat_beinit(), ProcSignalInit(), RegisterPostmasterChildActive(), replorigin_session_setup(), SharedInvalBackendInit(), StartupProcessMain(), WalReceiverMain(), and WalSummarizerMain().

◆ proc_exit()

void proc_exit ( int code )

Definition at line 104 of file ipc.c.

{
    /* not safe if forked by system(), etc. */
    if (MyProcPid != (int) getpid())
        elog(PANIC, "proc_exit() called in child process");
 
    /* Clean up everything that must be cleaned up */
    proc_exit_prepare(code);
 
#ifdef PROFILE_PID_DIR
    {
        /*
         * If we are profiling ourself then gprof's mcleanup() is about to
         * write out a profile to ./gmon.out.  Since mcleanup() always uses a
         * fixed file name, each backend will overwrite earlier profiles. To
         * fix that, we create a separate subdirectory for each backend
         * (./gprof/pid) and 'cd' to that subdirectory before we exit() - that
         * forces mcleanup() to write each profile into its own directory.  We
         * end up with something like: $PGDATA/gprof/8829/gmon.out
         * $PGDATA/gprof/8845/gmon.out ...
         *
         * To avoid undesirable disk space bloat, autovacuum workers are
         * discriminated against: all their gmon.out files go into the same
         * subdirectory.  Without this, an installation that is "just sitting
         * there" nonetheless eats megabytes of disk space every few seconds.
         *
         * Note that we do this here instead of in an on_proc_exit() callback
         * because we want to ensure that this code executes last - we don't
         * want to interfere with any other on_proc_exit() callback.  For the
         * same reason, we do not include it in proc_exit_prepare ... so if
         * you are exiting in the "wrong way" you won't drop your profile in a
         * nice place.
         */
        char        gprofDirName[32];
 
        if (AmAutoVacuumWorkerProcess())
            snprintf(gprofDirName, 32, "gprof/avworker");
        else
            snprintf(gprofDirName, 32, "gprof/%d", (int) getpid());
 
        /*
         * Use mkdir() instead of MakePGDirectory() since we aren't making a
         * PG directory here.
         */
        mkdir("gprof", S_IRWXU | S_IRWXG | S_IRWXO);
        mkdir(gprofDirName, S_IRWXU | S_IRWXG | S_IRWXO);
        chdir(gprofDirName);
    }
#endif
 
    elog(DEBUG3, "exit(%d)", code);
 
    exit(code);
}

References AmAutoVacuumWorkerProcess, DEBUG3, elog, exit(), mkdir, MyProcPid, PANIC, proc_exit_prepare(), S_IRWXG, S_IRWXO, S_IRWXU, and snprintf.

Referenced by apply_worker_exit(), ApplyWorkerMain(), auth_failed(), AutoVacWorkerMain(), BackendInitialize(), BackgroundWorkerMain(), BootstrapModeMain(), CheckerModeMain(), DisableSubscriptionAndExit(), errfinish(), ExitPostmaster(), HandleCheckpointerInterrupts(), HandleMainLoopInterrupts(), HandlePgArchInterrupts(), HandleStartupProcInterrupts(), HandleWalSummarizerInterrupts(), InitializeLogRepWorker(), maybe_reread_subscription(), PerformWalRecovery(), pg_attribute_noreturn(), PgArchiverMain(), PostgresMain(), PostgresSingleUserMain(), PreRestoreCommand(), process_syncing_tables_for_apply(), ProcessInterrupts(), ProcessParallelApplyInterrupts(), ProcessRepliesIfAny(), ProcessSlotSyncInterrupts(), ProcessStandbyMessage(), ReplSlotSyncWorkerMain(), RestoreArchivedFile(), slotsync_reread_config(), StartLogicalReplication(), StartReplication(), StartupProcessMain(), StartupProcShutdownHandler(), SysLoggerMain(), test_shm_mq_main(), WaitEventSetWaitBlock(), WalRcvWaitForStartPosition(), WalReceiverMain(), WalSndDone(), WalSndErrorCleanup(), WalSndWait(), and WalSummarizerMain().

◆ proc_exit_prepare()

static void proc_exit_prepare ( int code )

static

Definition at line 165 of file ipc.c.

{
    /*
     * Once we set this flag, we are committed to exit.  Any ereport() will
     * NOT send control back to the main loop, but right back here.
     */
    proc_exit_inprogress = true;
 
    /*
     * Forget any pending cancel or die requests; we're doing our best to
     * close up shop already.  Note that the signal handlers will not set
     * these flags again, now that proc_exit_inprogress is set.
     */
    InterruptPending = false;
    ProcDiePending = false;
    QueryCancelPending = false;
    InterruptHoldoffCount = 1;
    CritSectionCount = 0;
 
    /*
     * Also clear the error context stack, to prevent error callbacks from
     * being invoked by any elog/ereport calls made during proc_exit. Whatever
     * context they might want to offer is probably not relevant, and in any
     * case they are likely to fail outright after we've done things like
     * aborting any open transaction.  (In normal exit scenarios the context
     * stack should be empty anyway, but it might not be in the case of
     * elog(FATAL) for example.)
     */
    error_context_stack = NULL;
    /* For the same reason, reset debug_query_string before it's clobbered */
    debug_query_string = NULL;
 
    /* do our shared memory exits first */
    shmem_exit(code);
 
    elog(DEBUG3, "proc_exit(%d): %d callbacks to make",
         code, on_proc_exit_index);
 
    /*
     * call all the registered callbacks.
     *
     * Note that since we decrement on_proc_exit_index each time, if a
     * callback calls ereport(ERROR) or ereport(FATAL) then it won't be
     * invoked again when control comes back here (nor will the
     * previously-completed callbacks).  So, an infinite loop should not be
     * possible.
     */
    while (--on_proc_exit_index >= 0)
        on_proc_exit_list[on_proc_exit_index].function(code,
                                                       on_proc_exit_list[on_proc_exit_index].arg);
 
    on_proc_exit_index = 0;
}

References arg, CritSectionCount, DEBUG3, debug_query_string, elog, error_context_stack, ONEXIT::function, InterruptHoldoffCount, InterruptPending, on_proc_exit_index, on_proc_exit_list, proc_exit_inprogress, ProcDiePending, QueryCancelPending, and shmem_exit().

Referenced by atexit_callback(), and proc_exit().

◆ shmem_exit()

void shmem_exit ( int code )

Definition at line 228 of file ipc.c.

{
    shmem_exit_inprogress = true;
 
    /*
     * Call before_shmem_exit callbacks.
     *
     * These should be things that need most of the system to still be up and
     * working, such as cleanup of temp relations, which requires catalog
     * access; or things that need to be completed because later cleanup steps
     * depend on them, such as releasing lwlocks.
     */
    elog(DEBUG3, "shmem_exit(%d): %d before_shmem_exit callbacks to make",
         code, before_shmem_exit_index);
    while (--before_shmem_exit_index >= 0)
        before_shmem_exit_list[before_shmem_exit_index].function(code,
                                                                 before_shmem_exit_list[before_shmem_exit_index].arg);
    before_shmem_exit_index = 0;
 
    /*
     * Call dynamic shared memory callbacks.
     *
     * These serve the same purpose as late callbacks, but for dynamic shared
     * memory segments rather than the main shared memory segment.
     * dsm_backend_shutdown() has the same kind of progressive logic we use
     * for the main shared memory segment; namely, it unregisters each
     * callback before invoking it, so that we don't get stuck in an infinite
     * loop if one of those callbacks itself throws an ERROR or FATAL.
     *
     * Note that explicitly calling this function here is quite different from
     * registering it as an on_shmem_exit callback for precisely this reason:
     * if one dynamic shared memory callback errors out, the remaining
     * callbacks will still be invoked.  Thus, hard-coding this call puts it
     * equal footing with callbacks for the main shared memory segment.
     */
    dsm_backend_shutdown();
 
    /*
     * Call on_shmem_exit callbacks.
     *
     * These are generally releasing low-level shared memory resources.  In
     * some cases, this is a backstop against the possibility that the early
     * callbacks might themselves fail, leading to re-entry to this routine;
     * in other cases, it's cleanup that only happens at process exit.
     */
    elog(DEBUG3, "shmem_exit(%d): %d on_shmem_exit callbacks to make",
         code, on_shmem_exit_index);
    while (--on_shmem_exit_index >= 0)
        on_shmem_exit_list[on_shmem_exit_index].function(code,
                                                         on_shmem_exit_list[on_shmem_exit_index].arg);
    on_shmem_exit_index = 0;
 
    shmem_exit_inprogress = false;
}