1/*-------------------------------------------------------------------------
2 *
3 * dsm_impl.h
4 * low-level dynamic shared memory primitives
5 *
6 * Portions Copyright (c) 1996-2019, 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. */
42extern int dynamic_shared_memory_type;
43
44/*
45 * Directory for on-disk state.
46 *
47 * This is used by all implementations for crash recovery and by the mmap
48 * implementation for storage.
49 */
50#define PG_DYNSHMEM_DIR "pg_dynshmem"
51#define PG_DYNSHMEM_MMAP_FILE_PREFIX "mmap."
52
53/* A "name" for a dynamic shared memory segment. */
54typedef uint32 dsm_handle;
55
56/* All the shared-memory operations we know about. */
57typedef enum
58{
59 DSM_OP_CREATE,
60 DSM_OP_ATTACH,
61 DSM_OP_DETACH,
62 DSM_OP_DESTROY
63} dsm_op;
64
65/* Create, attach to, detach from, resize, or destroy a segment. */
66extern bool dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
67 void **impl_private, void **mapped_address, Size *mapped_size,
68 int elevel);
69
70/* Implementation-dependent actions required to keep segment until shutdown. */
71extern void dsm_impl_pin_segment(dsm_handle handle, void *impl_private,
72 void **impl_private_pm_handle);
73extern void dsm_impl_unpin_segment(dsm_handle handle, void **impl_private);
74
75#endif /* DSM_IMPL_H */
76