Line data    Source code

       1              : /*-------------------------------------------------------------------------
       2              :  * auxprocess.c
       3              :  *    functions related to auxiliary processes.
       4              :  *
       5              :  *
       6              :  * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
       7              :  * Portions Copyright (c) 1994, Regents of the University of California
       8              :  *
       9              :  * IDENTIFICATION
      10              :  *    src/backend/postmaster/auxprocess.c
      11              :  *-------------------------------------------------------------------------
      12              :  */
      13              : #include "postgres.h"
      14              : 
      15              : #include <unistd.h>
      16              : #include <signal.h>
      17              : 
      18              : #include "access/xlog.h"
      19              : #include "miscadmin.h"
      20              : #include "pgstat.h"
      21              : #include "postmaster/auxprocess.h"
      22              : #include "storage/condition_variable.h"
      23              : #include "storage/ipc.h"
      24              : #include "storage/proc.h"
      25              : #include "storage/procsignal.h"
      26              : #include "utils/memutils.h"
      27              : #include "utils/ps_status.h"
      28              : #include "utils/wait_event.h"
      29              : 
      30              : 
      31              : static void ShutdownAuxiliaryProcess(int code, Datum arg);
      32              : 
      33              : 
      34              : /*
      35              :  *   AuxiliaryProcessMainCommon
      36              :  *
      37              :  *   Common initialization code for auxiliary processes, such as the bgwriter,
      38              :  *   walwriter, walreceiver, and the startup process.
      39              :  */
      40              : void
      41         4903 : AuxiliaryProcessMainCommon(void)
      42              : {
      43              :     Assert(IsUnderPostmaster);
      44              : 
      45              :     /* Release postmaster's working memory context */
      46         4903 :     if (PostmasterContext)
      47              :     {
      48         4903 :         MemoryContextDelete(PostmasterContext);
      49         4903 :         PostmasterContext = NULL;
      50              :     }
      51              : 
      52         4903 :     init_ps_display(NULL);
      53              : 
      54              :     Assert(GetProcessingMode() == InitProcessing);
      55              : 
      56         4903 :     IgnoreSystemIndexes = true;
      57              : 
      58              :     /*
      59              :      * As an auxiliary process, we aren't going to do the full InitPostgres
      60              :      * pushups, but there are a couple of things that need to get lit up even
      61              :      * in an auxiliary process.
      62              :      */
      63              : 
      64              :     /*
      65              :      * Create a PGPROC so we can use LWLocks and access shared memory.
      66              :      */
      67         4903 :     InitAuxiliaryProcess();
      68              : 
      69         4903 :     BaseInit();
      70              : 
      71         4903 :     ProcSignalInit(NULL, 0);
      72              : 
      73              :     /*
      74              :      * Initialize a local cache of the data_checksum_version, to be updated by
      75              :      * the procsignal-based barriers.
      76              :      *
      77              :      * This intentionally happens after initializing the procsignal, otherwise
      78              :      * we might miss a state change. This means we can get a barrier for the
      79              :      * state we've just initialized - but it can happen only once.
      80              :      *
      81              :      * The postmaster (which is what gets forked into the new child process)
      82              :      * does not handle barriers, therefore it may not have the current value
      83              :      * of LocalDataChecksumVersion value (it'll have the value read from the
      84              :      * control file, which may be arbitrarily old).
      85              :      *
      86              :      * NB: Even if the postmaster handled barriers, the value might still be
      87              :      * stale, as it might have changed after this process forked.
      88              :      */
      89         4903 :     InitLocalDataChecksumState();
      90              : 
      91              :     /*
      92              :      * Auxiliary processes don't run transactions, but they may need a
      93              :      * resource owner anyway to manage buffer pins acquired outside
      94              :      * transactions (and, perhaps, other things in future).
      95              :      */
      96         4903 :     CreateAuxProcessResourceOwner();
      97              : 
      98              : 
      99              :     /* Initialize backend status information */
     100         4903 :     pgstat_beinit();
     101         4903 :     pgstat_bestart_initial();
     102         4903 :     pgstat_bestart_final();
     103              : 
     104              :     /* register a before-shutdown callback for LWLock cleanup */
     105         4903 :     before_shmem_exit(ShutdownAuxiliaryProcess, 0);
     106              : 
     107         4903 :     SetProcessingMode(NormalProcessing);
     108         4903 : }
     109              : 
     110              : /*
     111              :  * Begin shutdown of an auxiliary process.  This is approximately the equivalent
     112              :  * of ShutdownPostgres() in postinit.c.  We can't run transactions in an
     113              :  * auxiliary process, so most of the work of AbortTransaction() is not needed,
     114              :  * but we do need to make sure we've released any LWLocks we are holding.
     115              :  * (This is only critical during an error exit.)
     116              :  */
     117              : static void
     118         4903 : ShutdownAuxiliaryProcess(int code, Datum arg)
     119              : {
     120         4903 :     LWLockReleaseAll();
     121         4903 :     ConditionVariableCancelSleep();
     122         4903 :     pgstat_report_wait_end();
     123         4903 : }