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) 1996-2008, PostgreSQL Global Development Group
  12  * Portions Copyright (c) 1994, Regents of the University of California
  13  *
  14  * $PostgreSQL$
  15  *
  16  *-------------------------------------------------------------------------
  17  */
  18 #ifndef IPC_H
  19 #define IPC_H
  20
  21 typedef void (*pg_on_exit_callback) (int code, Datum arg);
  22
  23 /*----------
  24  * API for handling cleanup that must occur during either ereport(ERROR)
  25  * or ereport(FATAL) exits from a block of code.  (Typical examples are
  26  * undoing transient changes to shared-memory state.)
  27  *
  28  *              PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
  29  *              {
  30  *                      ... code that might throw ereport(ERROR) or ereport(FATAL) ...
  31  *              }
  32  *              PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
  33  *
  34  * where the cleanup code is in a function declared per pg_on_exit_callback.
  35  * The Datum value "arg" can carry any information the cleanup function
  36  * needs.
  37  *
  38  * This construct ensures that cleanup_function() will be called during
  39  * either ERROR or FATAL exits.  It will not be called on successful
  40  * exit from the controlled code.  (If you want it to happen then too,
  41  * call the function yourself from just after the construct.)
  42  *
  43  * Note: the macro arguments are multiply evaluated, so avoid side-effects.
  44  *----------
  45  */
  46 #define PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg)  \
  47         do { \
  48                 on_shmem_exit(cleanup_function, arg); \
  49                 PG_TRY()
  50
  51 #define PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg)  \
  52                 cancel_shmem_exit(cleanup_function, arg); \
  53                 PG_CATCH(); \
  54                 { \
  55                         cancel_shmem_exit(cleanup_function, arg); \
  56                         cleanup_function (0, arg); \
  57                         PG_RE_THROW(); \
  58                 } \
  59                 PG_END_TRY(); \
  60         } while (0)
  61
  62
  63 /* ipc.c */
  64 extern bool proc_exit_inprogress;
  65
  66 extern void proc_exit(int code);
  67 extern void shmem_exit(int code);
  68 extern void on_proc_exit(pg_on_exit_callback function, Datum arg);
  69 extern void on_shmem_exit(pg_on_exit_callback function, Datum arg);
  70 extern void cancel_shmem_exit(pg_on_exit_callback function, Datum arg);
  71 extern void on_exit_reset(void);
  72
  73 /* ipci.c */
  74 extern void CreateSharedMemoryAndSemaphores(bool makePrivate, int port);
  75
  76 #endif   /* IPC_H */