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2f932f71d9
postmaster startup scrutinizes any shared memory segment recorded in postmaster.pid, exiting if that segment matches the current data directory and has an attached process. When the postmaster.pid file was missing, a starting postmaster used weaker checks. Change to use the same checks in both scenarios. This increases the chance of a startup failure, in lieu of data corruption, if the DBA does "kill -9 `head -n1 postmaster.pid` && rm postmaster.pid && pg_ctl -w start". A postmaster will no longer recycle segments pertaining to other data directories. That's good for production, but it's bad for integration tests that crash a postmaster and immediately delete its data directory. Such a test now leaks a segment indefinitely. No "make check-world" test does that. win32_shmem.c already avoided all these problems. In 9.6 and later, enhance PostgresNode to facilitate testing. Back-patch to 9.4 (all supported versions). Reviewed by Daniel Gustafsson and Kyotaro HORIGUCHI. Discussion: https://postgr.es/m/20130911033341.GD225735@tornado.leadboat.com
90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_shmem.h
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* Platform-independent API for shared memory support.
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*
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* Every port is expected to support shared memory with approximately
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* SysV-ish semantics; in particular, a memory block is not anonymous
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* but has an ID, and we must be able to tell whether there are any
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* remaining processes attached to a block of a specified ID.
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*
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* To simplify life for the SysV implementation, the ID is assumed to
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* consist of two unsigned long values (these are key and ID in SysV
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* terms). Other platforms may ignore the second value if they need
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* only one ID number.
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*
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/pg_shmem.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PG_SHMEM_H
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#define PG_SHMEM_H
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#include "storage/dsm_impl.h"
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typedef struct PGShmemHeader /* standard header for all Postgres shmem */
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{
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int32 magic; /* magic # to identify Postgres segments */
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#define PGShmemMagic 679834894
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pid_t creatorPID; /* PID of creating process (set but unread) */
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Size totalsize; /* total size of segment */
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Size freeoffset; /* offset to first free space */
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dsm_handle dsm_control; /* ID of dynamic shared memory control seg */
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void *index; /* pointer to ShmemIndex table */
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#ifndef WIN32 /* Windows doesn't have useful inode#s */
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dev_t device; /* device data directory is on */
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ino_t inode; /* inode number of data directory */
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#endif
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} PGShmemHeader;
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/* GUC variables */
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extern int shared_memory_type;
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extern int huge_pages;
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/* Possible values for huge_pages */
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typedef enum
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{
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HUGE_PAGES_OFF,
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HUGE_PAGES_ON,
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HUGE_PAGES_TRY
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} HugePagesType;
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/* Possible values for shared_memory_type */
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typedef enum
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{
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SHMEM_TYPE_WINDOWS,
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SHMEM_TYPE_SYSV,
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SHMEM_TYPE_MMAP
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} PGShmemType;
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#ifndef WIN32
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extern unsigned long UsedShmemSegID;
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#else
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extern HANDLE UsedShmemSegID;
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#endif
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extern void *UsedShmemSegAddr;
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#if !defined(WIN32) && !defined(EXEC_BACKEND)
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_MMAP
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#elif !defined(WIN32)
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_SYSV
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#else
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_WINDOWS
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#endif
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#ifdef EXEC_BACKEND
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extern void PGSharedMemoryReAttach(void);
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extern void PGSharedMemoryNoReAttach(void);
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#endif
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extern PGShmemHeader *PGSharedMemoryCreate(Size size, int port,
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PGShmemHeader **shim);
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extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);
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extern void PGSharedMemoryDetach(void);
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#endif /* PG_SHMEM_H */
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