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Commit789a5b3

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Move attached to shared memory out into a separate function for clarity.
1 parent075a007 commit789a5b3

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1 file changed

+75
-68
lines changed

1 file changed

+75
-68
lines changed

‎src/backend/port/sysv_shmem.c

Lines changed: 75 additions & 68 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 1.9 2003/05/0814:49:03 momjian Exp $
13+
* $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.10 2003/05/0819:17:07 momjian Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -47,6 +47,8 @@ static void IpcMemoryDetach(int status, Datum shmaddr);
4747
staticvoidIpcMemoryDelete(intstatus,DatumshmId);
4848
staticvoid*PrivateMemoryCreate(uint32size);
4949
staticvoidPrivateMemoryDelete(intstatus,Datummemaddr);
50+
staticPGShmemHeader*PGSharedMemoryAttach(IpcMemoryKeykey,
51+
IpcMemoryId*shmid,void*addr);
5052

5153

5254
/*
@@ -297,72 +299,48 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
297299
IpcMemoryKeyNextShmemSegID;
298300
void*memAddress;
299301
PGShmemHeader*hdr;
302+
IpcMemoryIdshmid;
300303

301304
/* Room for a header? */
302305
Assert(size>MAXALIGN(sizeof(PGShmemHeader)));
303306

304-
if (ExecBackend&&UsedShmemSegID!=0)
305-
NextShmemSegID=UsedShmemSegID;
306-
else
307-
NextShmemSegID=port*1000+1;
308-
309-
for (;;NextShmemSegID++)
307+
/* Just attach and return the pointer */
308+
if (ExecBackend&&UsedShmemSegAddr!=NULL&& !makePrivate)
310309
{
311-
IpcMemoryIdshmid;
312-
313-
/* Special case if creating a private segment --- just malloc() it */
314-
if (makePrivate)
315-
{
316-
memAddress=PrivateMemoryCreate(size);
317-
break;
318-
}
319-
320-
/* If attach to fixed address, only try once */
321-
if (ExecBackend&&UsedShmemSegAddr!=NULL&&NextShmemSegID!=UsedShmemSegID)
310+
if ((hdr= (PGShmemHeader*)memAddress=PGSharedMemoryAttach(
311+
UsedShmemSegID,&shmid,UsedShmemSegAddr))==NULL)
322312
{
323-
fprintf(stderr,"Unable to attach to memory at fixed address: shmget(key=%d, addr=%p) failed: %s\n",
313+
fprintf(stderr,"Unable to attach topropermemory at fixed address: shmget(key=%d, addr=%p) failed: %s\n",
324314
(int)UsedShmemSegID,UsedShmemSegAddr,strerror(errno));
325315
proc_exit(1);
326316
}
317+
returnhdr;
318+
}
327319

328-
if (!ExecBackend||UsedShmemSegAddr==NULL)
329-
{
330-
/* Try to create new segment */
331-
memAddress=InternalIpcMemoryCreate(NextShmemSegID,size);
332-
if (memAddress)
333-
break;/* successful create and attach */
334-
}
335-
336-
/* See if it looks to be leftover from a dead Postgres process */
337-
shmid=shmget(NextShmemSegID,sizeof(PGShmemHeader),0);
338-
if (shmid<0)
339-
continue;/* failed: must be some other app's */
340-
341-
/* use intimate shared memory on SPARC Solaris */
342-
memAddress=shmat(shmid,UsedShmemSegAddr,
343-
#if defined(solaris)&&defined(__sparc__)
344-
SHM_SHARE_MMU
345-
#else
346-
0
347-
#endif
348-
);
349-
350-
if (memAddress== (void*)-1)
351-
continue;/* failed: must be some other app's */
320+
/* Create shared memory */
321+
322+
NextShmemSegID=port*1000+1;
352323

353-
hdr= (PGShmemHeader*)memAddress;
354-
if (hdr->magic!=PGShmemMagic)
324+
for (;;NextShmemSegID++)
325+
{
326+
/* Special case if creating a private segment --- just malloc() it */
327+
if (makePrivate)
355328
{
356-
shmdt(memAddress);
357-
continue;/* segment belongs to a non-Postgres app */
329+
memAddress=PrivateMemoryCreate(size);
330+
break;
358331
}
359332

360-
/* Successfully attached to shared memory, which is all we wanted */
361-
if (ExecBackend&&UsedShmemSegAddr!=NULL)
362-
break;
333+
/* Try to create new segment */
334+
memAddress=InternalIpcMemoryCreate(NextShmemSegID,size);
335+
if (memAddress)
336+
break;/* successful create and attach */
363337

364338
/* Check shared memory and possibly remove and recreate */
365339

340+
if ((hdr= (PGShmemHeader*)memAddress=PGSharedMemoryAttach(
341+
NextShmemSegID,&shmid,UsedShmemSegAddr))==NULL)
342+
continue;/* can't attach, not one of mine */
343+
366344
/*
367345
* If I am not the creator and it belongs to an extant process,
368346
* continue.
@@ -401,31 +379,60 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
401379
*/
402380
}
403381

382+
/*
383+
* OK, we created a new segment. Mark it as created by this process.
384+
* The order of assignments here is critical so that another Postgres
385+
* process can't see the header as valid but belonging to an invalid
386+
* PID!
387+
*/
404388
hdr= (PGShmemHeader*)memAddress;
389+
hdr->creatorPID=getpid();
390+
hdr->magic=PGShmemMagic;
405391

406-
if (!ExecBackend||makePrivate||UsedShmemSegAddr==NULL)
407-
{
408-
/*
409-
* OK, we created a new segment. Mark it as created by this process.
410-
* The order of assignments here is critical so that another Postgres
411-
* process can't see the header as valid but belonging to an invalid
412-
* PID!
413-
*/
414-
hdr->creatorPID=getpid();
415-
hdr->magic=PGShmemMagic;
416-
417-
/*
418-
* Initialize space allocation status for segment.
419-
*/
420-
hdr->totalsize=size;
421-
hdr->freeoffset=MAXALIGN(sizeof(PGShmemHeader));
422-
}
392+
/*
393+
* Initialize space allocation status for segment.
394+
*/
395+
hdr->totalsize=size;
396+
hdr->freeoffset=MAXALIGN(sizeof(PGShmemHeader));
423397

424-
if (ExecBackend&& !makePrivate&&UsedShmemSegAddr==NULL)
398+
399+
if (ExecBackend&&UsedShmemSegAddr==NULL&& !makePrivate)
425400
{
426401
UsedShmemSegAddr=memAddress;
427402
UsedShmemSegID=NextShmemSegID;
428403
}
404+
405+
returnhdr;
406+
}
407+
408+
409+
/*
410+
*Attach to shared memory and make sure it has a Postgres header
411+
*/
412+
staticPGShmemHeader*
413+
PGSharedMemoryAttach(IpcMemoryKeykey,IpcMemoryId*shmid,void*addr)
414+
{
415+
PGShmemHeader*hdr;
416+
417+
if ((*shmid=shmget(key,sizeof(PGShmemHeader),0))<0)
418+
returnNULL;
429419

420+
hdr= (PGShmemHeader*)shmat(*shmid,UsedShmemSegAddr,
421+
#if defined(solaris)&&defined(__sparc__)
422+
/* use intimate shared memory on SPARC Solaris */
423+
SHM_SHARE_MMU
424+
#else
425+
0
426+
#endif
427+
);
428+
429+
if (hdr== (PGShmemHeader*)-1)
430+
returnNULL;/* failed: must be some other app's */
431+
432+
if (hdr->magic!=PGShmemMagic)
433+
{
434+
shmdt(hdr);
435+
returnNULL;/* segment belongs to a non-Postgres app */
436+
}
430437
returnhdr;
431438
}

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