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Commitf8a769b

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Cause stats processes to detach from shared memory when started, so that
they do not prevent the postmaster from deleting the shmem segment duringa post-backend-crash restart cycle. Per recent discussion.
1 parent7e4a629 commitf8a769b

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3 files changed

+35
-11
lines changed

3 files changed

+35
-11
lines changed

‎src/backend/port/sysv_shmem.c

Lines changed: 28 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
* Portions Copyright (c) 1994, Regents of the University of California
1111
*
1212
* IDENTIFICATION
13-
* $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.24 2003/10/27 18:30:07 momjian Exp $
13+
* $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.25 2003/11/07 21:55:49 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -134,7 +134,7 @@ InternalIpcMemoryCreate(IpcMemoryKey memKey, uint32 size)
134134

135135
/* OK, should be able to attach to the segment */
136136
#ifdefSHM_SHARE_MMU
137-
/* use intimate shared memory onSPARCSolaris */
137+
/* use intimate shared memory on Solaris */
138138
memAddress=shmat(shmid,0,SHM_SHARE_MMU);
139139
#else
140140
memAddress=shmat(shmid,0,0);
@@ -244,7 +244,7 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
244244
/* Room for a header? */
245245
Assert(size>MAXALIGN(sizeof(PGShmemHeader)));
246246

247-
/*Just attach and return the pointer */
247+
/*If Exec case, just attach and return the pointer */
248248
if (ExecBackend&&UsedShmemSegAddr!=NULL&& !makePrivate)
249249
{
250250
if ((hdr=PGSharedMemoryAttach(UsedShmemSegID,&shmid))==NULL)
@@ -253,6 +253,9 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
253253
returnhdr;
254254
}
255255

256+
/* Make sure PGSharedMemoryAttach doesn't fail without need */
257+
UsedShmemSegAddr=NULL;
258+
256259
/* Loop till we find a free IPC key */
257260
NextShmemSegID=port*1000;
258261

@@ -326,16 +329,32 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
326329
hdr->totalsize=size;
327330
hdr->freeoffset=MAXALIGN(sizeof(PGShmemHeader));
328331

329-
330-
if (ExecBackend&&UsedShmemSegAddr==NULL&& !makePrivate)
331-
{
332-
UsedShmemSegAddr=memAddress;
333-
UsedShmemSegID=NextShmemSegID;
334-
}
332+
/* Save info for possible future use */
333+
UsedShmemSegAddr=memAddress;
334+
UsedShmemSegID=NextShmemSegID;
335335

336336
returnhdr;
337337
}
338338

339+
/*
340+
* PGSharedMemoryDetach
341+
*
342+
* Detach from the shared memory segment, if still attached. This is not
343+
* intended for use by the process that originally created the segment
344+
* (it will have an on_shmem_exit callback registered to do that). Rather,
345+
* this is for subprocesses that have inherited an attachment and want to
346+
* get rid of it.
347+
*/
348+
void
349+
PGSharedMemoryDetach(void)
350+
{
351+
if (UsedShmemSegAddr!=NULL)
352+
{
353+
if (shmdt(UsedShmemSegAddr)<0)
354+
elog(LOG,"shmdt(%p) failed: %m",UsedShmemSegAddr);
355+
UsedShmemSegAddr=NULL;
356+
}
357+
}
339358

340359
/*
341360
* Attach to shared memory and make sure it has a Postgres header

‎src/backend/postmaster/pgstat.c

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*Copyright (c) 2001-2003, PostgreSQL Global Development Group
1515
*
16-
*$Header: /cvsroot/pgsql/src/backend/postmaster/pgstat.c,v 1.45 2003/09/25 06:58:01 petere Exp $
16+
*$Header: /cvsroot/pgsql/src/backend/postmaster/pgstat.c,v 1.46 2003/11/07 21:55:50 tgl Exp $
1717
* ----------
1818
*/
1919
#include"postgres.h"
@@ -44,6 +44,7 @@
4444
#include"utils/memutils.h"
4545
#include"storage/backendid.h"
4646
#include"storage/ipc.h"
47+
#include"storage/pg_shmem.h"
4748
#include"utils/rel.h"
4849
#include"utils/hsearch.h"
4950
#include"utils/ps_status.h"
@@ -400,6 +401,9 @@ pgstat_start(void)
400401
/* Close the postmaster's sockets, except for pgstat link */
401402
ClosePostmasterPorts(false);
402403

404+
/* Drop our connection to postmaster's shared memory, as well */
405+
PGSharedMemoryDetach();
406+
403407
pgstat_main();
404408

405409
exit(0);

‎src/include/storage/pg_shmem.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -17,7 +17,7 @@
1717
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
1818
* Portions Copyright (c) 1994, Regents of the University of California
1919
*
20-
* $Id: pg_shmem.h,v 1.7 2003/08/04 02:40:15 momjian Exp $
20+
* $Id: pg_shmem.h,v 1.8 2003/11/07 21:55:50 tgl Exp $
2121
*
2222
*-------------------------------------------------------------------------
2323
*/
@@ -44,5 +44,6 @@ extern void *UsedShmemSegAddr;
4444
externPGShmemHeader*PGSharedMemoryCreate(uint32size,boolmakePrivate,
4545
intport);
4646
externboolPGSharedMemoryIsInUse(unsigned longid1,unsigned longid2);
47+
externvoidPGSharedMemoryDetach(void);
4748

4849
#endif/* PG_SHMEM_H */

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