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Consistently test for in-use shared memory.

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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
This commit is contained in:
Noah Misch
2019-04-03 17:03:46 -07:00
parent af052daec5
commit 2f932f71d9
11 changed files with 470 additions and 179 deletions
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2
src/include/storage/ipc.h
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@@ -76,6 +76,6 @@ extern void on_exit_reset(void);
/* ipci.c */
extern PGDLLIMPORT shmem_startup_hook_type shmem_startup_hook;
extern void CreateSharedMemoryAndSemaphores(bool makePrivate, int port);
extern void CreateSharedMemoryAndSemaphores(int port);
#endif /* IPC_H */

6
src/include/storage/pg_shmem.h
View File

@@ -30,7 +30,7 @@ typedef struct PGShmemHeader /* standard header for all Postgres shmem */
{
int32 magic; /* magic # to identify Postgres segments */
#define PGShmemMagic 679834894
pid_t creatorPID; /* PID of creating process */
pid_t creatorPID; /* PID of creating process (set but unread) */
Size totalsize; /* total size of segment */
Size freeoffset; /* offset to first free space */
dsm_handle dsm_control; /* ID of dynamic shared memory control seg */
@@ -81,8 +81,8 @@ extern void PGSharedMemoryReAttach(void);
extern void PGSharedMemoryNoReAttach(void);
#endif
extern PGShmemHeader *PGSharedMemoryCreate(Size size, bool makePrivate,
int port, PGShmemHeader **shim);
extern PGShmemHeader *PGSharedMemoryCreate(Size size, int port,
PGShmemHeader **shim);
extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);
extern void PGSharedMemoryDetach(void);