src/include/storage/ipc.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * ipc.h
   4  *        POSTGRES inter-process communication definitions.
   5  *
   6  * This file is misnamed, as it no longer has much of anything directly
   7  * to do with IPC.  The functionality here is concerned with managing
   8  * exit-time cleanup for either a postmaster or a backend.
   9  *
  10  *
  11  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  12  * Portions Copyright (c) 1994, Regents of the University of California
  13  *
  14  * src/include/storage/ipc.h
  15  *
  16  *-------------------------------------------------------------------------
  17  */
  18 #ifndef IPC_H
  19 #define IPC_H
  20
  21 typedef void (*pg_on_exit_callback) (int code, Datum arg);
  22 typedef void (*shmem_startup_hook_type) (void);
  23
  24 /*----------
  25  * API for handling cleanup that must occur during either ereport(ERROR)
  26  * or ereport(FATAL) exits from a block of code.  (Typical examples are
  27  * undoing transient changes to shared-memory state.)
  28  *
  29  *              PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
  30  *              {
  31  *                      ... code that might throw ereport(ERROR) or ereport(FATAL) ...
  32  *              }
  33  *              PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
  34  *
  35  * where the cleanup code is in a function declared per pg_on_exit_callback.
  36  * The Datum value "arg" can carry any information the cleanup function
  37  * needs.
  38  *
  39  * This construct ensures that cleanup_function() will be called during
  40  * either ERROR or FATAL exits.  It will not be called on successful
  41  * exit from the controlled code.  (If you want it to happen then too,
  42  * call the function yourself from just after the construct.)
  43  *
  44  * Note: the macro arguments are multiply evaluated, so avoid side-effects.
  45  *----------
  46  */
  47 #define PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg)  \
  48         do { \
  49                 before_shmem_exit(cleanup_function, arg); \
  50                 PG_TRY()
  51
  52 #define PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg)      \
  53                 cancel_before_shmem_exit(cleanup_function, arg); \
  54                 PG_CATCH(); \
  55                 { \
  56                         cancel_before_shmem_exit(cleanup_function, arg); \
  57                         cleanup_function (0, arg); \
  58                         PG_RE_THROW(); \
  59                 } \
  60                 PG_END_TRY(); \
  61         } while (0)
  62
  63
  64 /* ipc.c */
  65 extern PGDLLIMPORT bool proc_exit_inprogress;
  66 extern PGDLLIMPORT bool shmem_exit_inprogress;
  67
  68 extern void proc_exit(int code) pg_attribute_noreturn();
  69 extern void shmem_exit(int code);
  70 extern void on_proc_exit(pg_on_exit_callback function, Datum arg);
  71 extern void on_shmem_exit(pg_on_exit_callback function, Datum arg);
  72 extern void before_shmem_exit(pg_on_exit_callback function, Datum arg);
  73 extern void cancel_before_shmem_exit(pg_on_exit_callback function, Datum arg);
  74 extern void on_exit_reset(void);
  75 extern void check_on_shmem_exit_lists_are_empty(void);
  76
  77 /* ipci.c */
  78 extern PGDLLIMPORT shmem_startup_hook_type shmem_startup_hook;
  79
  80 extern Size CalculateShmemSize(int *num_semaphores);
  81 extern void CreateSharedMemoryAndSemaphores(void);
  82 extern void InitializeShmemGUCs(void);
  83
  84 #endif                                                  /* IPC_H */