src/include/storage/dsm_impl.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * dsm_impl.h
   4  *        low-level dynamic shared memory primitives
   5  *
   6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * src/include/storage/dsm_impl.h
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #ifndef DSM_IMPL_H
  14 #define DSM_IMPL_H
  15
  16 /* Dynamic shared memory implementations. */
  17 #define DSM_IMPL_POSIX                  1
  18 #define DSM_IMPL_SYSV                   2
  19 #define DSM_IMPL_WINDOWS                3
  20 #define DSM_IMPL_MMAP                   4
  21
  22 /*
  23  * Determine which dynamic shared memory implementations will be supported
  24  * on this platform, and which one will be the default.
  25  */
  26 #ifdef WIN32
  27 #define USE_DSM_WINDOWS
  28 #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE              DSM_IMPL_WINDOWS
  29 #else
  30 #ifdef HAVE_SHM_OPEN
  31 #define USE_DSM_POSIX
  32 #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE              DSM_IMPL_POSIX
  33 #endif
  34 #define USE_DSM_SYSV
  35 #ifndef DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE
  36 #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE              DSM_IMPL_SYSV
  37 #endif
  38 #define USE_DSM_MMAP
  39 #endif
  40
  41 /* GUC. */
  42 extern PGDLLIMPORT int dynamic_shared_memory_type;
  43 extern PGDLLIMPORT int min_dynamic_shared_memory;
  44
  45 /*
  46  * Directory for on-disk state.
  47  *
  48  * This is used by all implementations for crash recovery and by the mmap
  49  * implementation for storage.
  50  */
  51 #define PG_DYNSHMEM_DIR                                 "pg_dynshmem"
  52 #define PG_DYNSHMEM_MMAP_FILE_PREFIX    "mmap."
  53
  54 /* A "name" for a dynamic shared memory segment. */
  55 typedef uint32 dsm_handle;
  56
  57 /* Sentinel value to use for invalid DSM handles. */
  58 #define DSM_HANDLE_INVALID ((dsm_handle) 0)
  59
  60 /* All the shared-memory operations we know about. */
  61 typedef enum
  62 {
  63         DSM_OP_CREATE,
  64         DSM_OP_ATTACH,
  65         DSM_OP_DETACH,
  66         DSM_OP_DESTROY,
  67 } dsm_op;
  68
  69 /* Create, attach to, detach from, resize, or destroy a segment. */
  70 extern bool dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
  71                                                 void **impl_private, void **mapped_address, Size *mapped_size,
  72                                                 int elevel);
  73
  74 /* Implementation-dependent actions required to keep segment until shutdown. */
  75 extern void dsm_impl_pin_segment(dsm_handle handle, void *impl_private,
  76                                                                  void **impl_private_pm_handle);
  77 extern void dsm_impl_unpin_segment(dsm_handle handle, void **impl_private);
  78
  79 #endif                                                  /* DSM_IMPL_H */