path: root/0003-Disable-shm.patch

--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -119,161 +119,7 @@
 static void *
 InternalIpcMemoryCreate(IpcMemoryKey memKey, Size size)
 {
-	IpcMemoryId shmid;
-	void	   *requestedAddress = NULL;
-	void	   *memAddress;
-
-	/*
-	 * Normally we just pass requestedAddress = NULL to shmat(), allowing the
-	 * system to choose where the segment gets mapped.  But in an EXEC_BACKEND
-	 * build, it's possible for whatever is chosen in the postmaster to not
-	 * work for backends, due to variations in address space layout.  As a
-	 * rather klugy workaround, allow the user to specify the address to use
-	 * via setting the environment variable PG_SHMEM_ADDR.  (If this were of
-	 * interest for anything except debugging, we'd probably create a cleaner
-	 * and better-documented way to set it, such as a GUC.)
-	 */
-#ifdef EXEC_BACKEND
-	{
-		char	   *pg_shmem_addr = getenv("PG_SHMEM_ADDR");
-
-		if (pg_shmem_addr)
-			requestedAddress = (void *) strtoul(pg_shmem_addr, NULL, 0);
-		else
-		{
-#if defined(__darwin__) && SIZEOF_VOID_P == 8
-			/*
-			 * Provide a default value that is believed to avoid problems with
-			 * ASLR on the current macOS release.
-			 */
-			requestedAddress = (void *) 0x80000000000;
-#endif
-		}
-	}
-#endif
-
-	shmid = shmget(memKey, size, IPC_CREAT | IPC_EXCL | IPCProtection);
-
-	if (shmid < 0)
-	{
-		int			shmget_errno = errno;
-
-		/*
-		 * Fail quietly if error indicates a collision with existing segment.
-		 * One would expect EEXIST, given that we said IPC_EXCL, but perhaps
-		 * we could get a permission violation instead?  Also, EIDRM might
-		 * occur if an old seg is slated for destruction but not gone yet.
-		 */
-		if (shmget_errno == EEXIST || shmget_errno == EACCES
-#ifdef EIDRM
-			|| shmget_errno == EIDRM
-#endif
-			)
-			return NULL;
-
-		/*
-		 * Some BSD-derived kernels are known to return EINVAL, not EEXIST, if
-		 * there is an existing segment but it's smaller than "size" (this is
-		 * a result of poorly-thought-out ordering of error tests). To
-		 * distinguish between collision and invalid size in such cases, we
-		 * make a second try with size = 0.  These kernels do not test size
-		 * against SHMMIN in the preexisting-segment case, so we will not get
-		 * EINVAL a second time if there is such a segment.
-		 */
-		if (shmget_errno == EINVAL)
-		{
-			shmid = shmget(memKey, 0, IPC_CREAT | IPC_EXCL | IPCProtection);
-
-			if (shmid < 0)
-			{
-				/* As above, fail quietly if we verify a collision */
-				if (errno == EEXIST || errno == EACCES
-#ifdef EIDRM
-					|| errno == EIDRM
-#endif
-					)
 					return NULL;
-				/* Otherwise, fall through to report the original error */
-			}
-			else
-			{
-				/*
-				 * On most platforms we cannot get here because SHMMIN is
-				 * greater than zero.  However, if we do succeed in creating a
-				 * zero-size segment, free it and then fall through to report
-				 * the original error.
-				 */
-				if (shmctl(shmid, IPC_RMID, NULL) < 0)
-					elog(LOG, "shmctl(%d, %d, 0) failed: %m",
-						 (int) shmid, IPC_RMID);
-			}
-		}
-
-		/*
-		 * Else complain and abort.
-		 *
-		 * Note: at this point EINVAL should mean that either SHMMIN or SHMMAX
-		 * is violated.  SHMALL violation might be reported as either ENOMEM
-		 * (BSDen) or ENOSPC (Linux); the Single Unix Spec fails to say which
-		 * it should be.  SHMMNI violation is ENOSPC, per spec.  Just plain
-		 * not-enough-RAM is ENOMEM.
-		 */
-		errno = shmget_errno;
-		ereport(FATAL,
-				(errmsg("could not create shared memory segment: %m"),
-				 errdetail("Failed system call was shmget(key=%lu, size=%zu, 0%o).",
-						   (unsigned long) memKey, size,
-						   IPC_CREAT | IPC_EXCL | IPCProtection),
-				 (shmget_errno == EINVAL) ?
-				 errhint("This error usually means that PostgreSQL's request for a shared memory "
-						 "segment exceeded your kernel's SHMMAX parameter, or possibly that "
-						 "it is less than "
-						 "your kernel's SHMMIN parameter.\n"
-						 "The PostgreSQL documentation contains more information about shared "
-						 "memory configuration.") : 0,
-				 (shmget_errno == ENOMEM) ?
-				 errhint("This error usually means that PostgreSQL's request for a shared "
-						 "memory segment exceeded your kernel's SHMALL parameter.  You might need "
-						 "to reconfigure the kernel with larger SHMALL.\n"
-						 "The PostgreSQL documentation contains more information about shared "
-						 "memory configuration.") : 0,
-				 (shmget_errno == ENOSPC) ?
-				 errhint("This error does *not* mean that you have run out of disk space.  "
-						 "It occurs either if all available shared memory IDs have been taken, "
-						 "in which case you need to raise the SHMMNI parameter in your kernel, "
-						 "or because the system's overall limit for shared memory has been "
-						 "reached.\n"
-						 "The PostgreSQL documentation contains more information about shared "
-						 "memory configuration.") : 0));
-	}
-
-	/* Register on-exit routine to delete the new segment */
-	on_shmem_exit(IpcMemoryDelete, Int32GetDatum(shmid));
-
-	/* OK, should be able to attach to the segment */
-	memAddress = shmat(shmid, requestedAddress, PG_SHMAT_FLAGS);
-
-	if (memAddress == (void *) -1)
-		elog(FATAL, "shmat(id=%d, addr=%p, flags=0x%x) failed: %m",
-			 shmid, requestedAddress, PG_SHMAT_FLAGS);
-
-	/* Register on-exit routine to detach new segment before deleting */
-	on_shmem_exit(IpcMemoryDetach, PointerGetDatum(memAddress));
-
-	/*
-	 * Store shmem key and ID in data directory lockfile.  Format to try to
-	 * keep it the same length always (trailing junk in the lockfile won't
-	 * hurt, but might confuse humans).
-	 */
-	{
-		char		line[64];
-
-		sprintf(line, "%9lu %9lu",
-				(unsigned long) memKey, (unsigned long) shmid);
-		AddToDataDirLockFile(LOCK_FILE_LINE_SHMEM_KEY, line);
-	}
-
-	return memAddress;
 }
 
 /****************************************************************************/
@@ -285,7 +131,6 @@
 IpcMemoryDetach(int status, Datum shmaddr)
 {
 	/* Detach System V shared memory block. */
-	if (shmdt((void *) DatumGetPointer(shmaddr)) < 0)
 		elog(LOG, "shmdt(%p) failed: %m", DatumGetPointer(shmaddr));
 }
 
@@ -296,7 +141,6 @@
 static void
 IpcMemoryDelete(int status, Datum shmId)
 {
-	if (shmctl(DatumGetInt32(shmId), IPC_RMID, NULL) < 0)
 		elog(LOG, "shmctl(%d, %d, 0) failed: %m",
 			 DatumGetInt32(shmId), IPC_RMID);
 }
@@ -315,23 +159,8 @@
 bool
 PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2)
 {
-	PGShmemHeader *memAddress;
-	IpcMemoryState state;
-
-	state = PGSharedMemoryAttach((IpcMemoryId) id2, NULL, &memAddress);
-	if (memAddress && shmdt((void *) memAddress) < 0)
-		elog(LOG, "shmdt(%p) failed: %m", memAddress);
-	switch (state)
-	{
-		case SHMSTATE_ENOENT:
-		case SHMSTATE_FOREIGN:
-		case SHMSTATE_UNATTACHED:
+	elog(LOG, "shmdt(%p) failed: %m", NULL);
 			return false;
-		case SHMSTATE_ANALYSIS_FAILURE:
-		case SHMSTATE_ATTACHED:
-			return true;
-	}
-	return true;
 }
 
 /*
@@ -347,109 +176,9 @@
 					 void *attachAt,
 					 PGShmemHeader **addr)
 {
-	struct shmid_ds shmStat;
-	struct stat statbuf;
-	PGShmemHeader *hdr;
-
 	*addr = NULL;
 
-	/*
-	 * First, try to stat the shm segment ID, to see if it exists at all.
-	 */
-	if (shmctl(shmId, IPC_STAT, &shmStat) < 0)
-	{
-		/*
-		 * EINVAL actually has multiple possible causes documented in the
-		 * shmctl man page, but we assume it must mean the segment no longer
-		 * exists.
-		 */
-		if (errno == EINVAL)
-			return SHMSTATE_ENOENT;
-
-		/*
-		 * EACCES implies we have no read permission, which means it is not a
-		 * Postgres shmem segment (or at least, not one that is relevant to
-		 * our data directory).
-		 */
-		if (errno == EACCES)
 			return SHMSTATE_FOREIGN;
-
-		/*
-		 * Some Linux kernel versions (in fact, all of them as of July 2007)
-		 * sometimes return EIDRM when EINVAL is correct.  The Linux kernel
-		 * actually does not have any internal state that would justify
-		 * returning EIDRM, so we can get away with assuming that EIDRM is
-		 * equivalent to EINVAL on that platform.
-		 */
-#ifdef HAVE_LINUX_EIDRM_BUG
-		if (errno == EIDRM)
-			return SHMSTATE_ENOENT;
-#endif
-
-		/*
-		 * Otherwise, we had better assume that the segment is in use.  The
-		 * only likely case is (non-Linux, assumed spec-compliant) EIDRM,
-		 * which implies that the segment has been IPC_RMID'd but there are
-		 * still processes attached to it.
-		 */
-		return SHMSTATE_ANALYSIS_FAILURE;
-	}
-
-	/*
-	 * Try to attach to the segment and see if it matches our data directory.
-	 * This avoids any risk of duplicate-shmem-key conflicts on machines that
-	 * are running several postmasters under the same userid.
-	 *
-	 * (When we're called from PGSharedMemoryCreate, this stat call is
-	 * duplicative; but since this isn't a high-traffic case it's not worth
-	 * trying to optimize.)
-	 */
-	if (stat(DataDir, &statbuf) < 0)
-		return SHMSTATE_ANALYSIS_FAILURE;	/* can't stat; be conservative */
-
-	hdr = (PGShmemHeader *) shmat(shmId, attachAt, PG_SHMAT_FLAGS);
-	if (hdr == (PGShmemHeader *) -1)
-	{
-		/*
-		 * Attachment failed.  The cases we're interested in are the same as
-		 * for the shmctl() call above.  In particular, note that the owning
-		 * postmaster could have terminated and removed the segment between
-		 * shmctl() and shmat().
-		 *
-		 * If attachAt isn't NULL, it's possible that EINVAL reflects a
-		 * problem with that address not a vanished segment, so it's best to
-		 * pass NULL when probing for conflicting segments.
-		 */
-		if (errno == EINVAL)
-			return SHMSTATE_ENOENT; /* segment disappeared */
-		if (errno == EACCES)
-			return SHMSTATE_FOREIGN;	/* must be non-Postgres */
-#ifdef HAVE_LINUX_EIDRM_BUG
-		if (errno == EIDRM)
-			return SHMSTATE_ENOENT; /* segment disappeared */
-#endif
-		/* Otherwise, be conservative. */
-		return SHMSTATE_ANALYSIS_FAILURE;
-	}
-	*addr = hdr;
-
-	if (hdr->magic != PGShmemMagic ||
-		hdr->device != statbuf.st_dev ||
-		hdr->inode != statbuf.st_ino)
-	{
-		/*
-		 * It's either not a Postgres segment, or not one for my data
-		 * directory.
-		 */
-		return SHMSTATE_FOREIGN;
-	}
-
-	/*
-	 * It does match our data directory, so now test whether any processes are
-	 * still attached to it.  (We are, now, but the shm_nattch result is from
-	 * before we attached to it.)
-	 */
-	return shmStat.shm_nattch == 0 ? SHMSTATE_UNATTACHED : SHMSTATE_ATTACHED;
 }
 
 /*
@@ -691,170 +420,8 @@
 PGSharedMemoryCreate(Size size,
 					 PGShmemHeader **shim)
 {
-	IpcMemoryKey NextShmemSegID;
-	void	   *memAddress;
-	PGShmemHeader *hdr;
-	struct stat statbuf;
-	Size		sysvsize;
-
-	/*
-	 * We use the data directory's ID info (inode and device numbers) to
-	 * positively identify shmem segments associated with this data dir, and
-	 * also as seeds for searching for a free shmem key.
-	 */
-	if (stat(DataDir, &statbuf) < 0)
-		ereport(FATAL,
-				(errcode_for_file_access(),
-				 errmsg("could not stat data directory \"%s\": %m",
-						DataDir)));
-
-	/* Complain if hugepages demanded but we can't possibly support them */
-#if !defined(MAP_HUGETLB)
-	if (huge_pages == HUGE_PAGES_ON)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("huge pages not supported on this platform")));
-#endif
-
-	/* For now, we don't support huge pages in SysV memory */
-	if (huge_pages == HUGE_PAGES_ON && shared_memory_type != SHMEM_TYPE_MMAP)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("huge pages not supported with the current shared_memory_type setting")));
-
-	/* Room for a header? */
-	Assert(size > MAXALIGN(sizeof(PGShmemHeader)));
-
-	if (shared_memory_type == SHMEM_TYPE_MMAP)
-	{
-		AnonymousShmem = CreateAnonymousSegment(&size);
-		AnonymousShmemSize = size;
-
-		/* Register on-exit routine to unmap the anonymous segment */
-		on_shmem_exit(AnonymousShmemDetach, (Datum) 0);
-
-		/* Now we need only allocate a minimal-sized SysV shmem block. */
-		sysvsize = sizeof(PGShmemHeader);
-	}
-	else
-		sysvsize = size;
-
-	/*
-	 * Loop till we find a free IPC key.  Trust CreateDataDirLockFile() to
-	 * ensure no more than one postmaster per data directory can enter this
-	 * loop simultaneously.  (CreateDataDirLockFile() does not entirely ensure
-	 * that, but prefer fixing it over coping here.)
-	 */
-	NextShmemSegID = statbuf.st_ino;
-
-	for (;;)
-	{
-		IpcMemoryId shmid;
-		PGShmemHeader *oldhdr;
-		IpcMemoryState state;
-
-		/* Try to create new segment */
-		memAddress = InternalIpcMemoryCreate(NextShmemSegID, sysvsize);
-		if (memAddress)
-			break;				/* successful create and attach */
-
-		/* Check shared memory and possibly remove and recreate */
-
-		/*
-		 * shmget() failure is typically EACCES, hence SHMSTATE_FOREIGN.
-		 * ENOENT, a narrow possibility, implies SHMSTATE_ENOENT, but one can
-		 * safely treat SHMSTATE_ENOENT like SHMSTATE_FOREIGN.
-		 */
-		shmid = shmget(NextShmemSegID, sizeof(PGShmemHeader), 0);
-		if (shmid < 0)
-		{
-			oldhdr = NULL;
-			state = SHMSTATE_FOREIGN;
-		}
-		else
-			state = PGSharedMemoryAttach(shmid, NULL, &oldhdr);
-
-		switch (state)
-		{
-			case SHMSTATE_ANALYSIS_FAILURE:
-			case SHMSTATE_ATTACHED:
-				ereport(FATAL,
-						(errcode(ERRCODE_LOCK_FILE_EXISTS),
-						 errmsg("pre-existing shared memory block (key %lu, ID %lu) is still in use",
-								(unsigned long) NextShmemSegID,
-								(unsigned long) shmid),
-						 errhint("Terminate any old server processes associated with data directory \"%s\".",
-								 DataDir)));
-				break;
-			case SHMSTATE_ENOENT:
-
-				/*
-				 * To our surprise, some other process deleted since our last
-				 * InternalIpcMemoryCreate().  Moments earlier, we would have
-				 * seen SHMSTATE_FOREIGN.  Try that same ID again.
-				 */
-				elog(LOG,
-					 "shared memory block (key %lu, ID %lu) deleted during startup",
-					 (unsigned long) NextShmemSegID,
-					 (unsigned long) shmid);
-				break;
-			case SHMSTATE_FOREIGN:
-				NextShmemSegID++;
-				break;
-			case SHMSTATE_UNATTACHED:
-
-				/*
-				 * The segment pertains to DataDir, and every process that had
-				 * used it has died or detached.  Zap it, if possible, and any
-				 * associated dynamic shared memory segments, as well.  This
-				 * shouldn't fail, but if it does, assume the segment belongs
-				 * to someone else after all, and try the next candidate.
-				 * Otherwise, try again to create the segment.  That may fail
-				 * if some other process creates the same shmem key before we
-				 * do, in which case we'll try the next key.
-				 */
-				if (oldhdr->dsm_control != 0)
-					dsm_cleanup_using_control_segment(oldhdr->dsm_control);
-				if (shmctl(shmid, IPC_RMID, NULL) < 0)
-					NextShmemSegID++;
-				break;
-		}
-
-		if (oldhdr && shmdt((void *) oldhdr) < 0)
-			elog(LOG, "shmdt(%p) failed: %m", oldhdr);
-	}
-
-	/* Initialize new segment. */
-	hdr = (PGShmemHeader *) memAddress;
-	hdr->creatorPID = getpid();
-	hdr->magic = PGShmemMagic;
-	hdr->dsm_control = 0;
-
-	/* Fill in the data directory ID info, too */
-	hdr->device = statbuf.st_dev;
-	hdr->inode = statbuf.st_ino;
-
-	/*
-	 * Initialize space allocation status for segment.
-	 */
-	hdr->totalsize = size;
-	hdr->freeoffset = MAXALIGN(sizeof(PGShmemHeader));
-	*shim = hdr;
-
-	/* Save info for possible future use */
-	UsedShmemSegAddr = memAddress;
-	UsedShmemSegID = (unsigned long) NextShmemSegID;
-
-	/*
-	 * If AnonymousShmem is NULL here, then we're not using anonymous shared
-	 * memory, and should return a pointer to the System V shared memory
-	 * block. Otherwise, the System V shared memory block is only a shim, and
-	 * we must return a pointer to the real block.
-	 */
-	if (AnonymousShmem == NULL)
-		return hdr;
-	memcpy(AnonymousShmem, hdr, sizeof(PGShmemHeader));
-	return (PGShmemHeader *) AnonymousShmem;
+	*shim = NULL;
+	return NULL;
 }
 
 #ifdef EXEC_BACKEND
@@ -874,27 +441,13 @@
 void
 PGSharedMemoryReAttach(void)
 {
-	IpcMemoryId shmid;
-	PGShmemHeader *hdr;
-	IpcMemoryState state;
+	PGShmemHeader *hdr = NULL;
 	void	   *origUsedShmemSegAddr = UsedShmemSegAddr;
 
 	Assert(UsedShmemSegAddr != NULL);
 	Assert(IsUnderPostmaster);
 
-#ifdef __CYGWIN__
-	/* cygipc (currently) appears to not detach on exec. */
-	PGSharedMemoryDetach();
-	UsedShmemSegAddr = origUsedShmemSegAddr;
-#endif
-
 	elog(DEBUG3, "attaching to %p", UsedShmemSegAddr);
-	shmid = shmget(UsedShmemSegID, sizeof(PGShmemHeader), 0);
-	if (shmid < 0)
-		state = SHMSTATE_FOREIGN;
-	else
-		state = PGSharedMemoryAttach(shmid, UsedShmemSegAddr, &hdr);
-	if (state != SHMSTATE_ATTACHED)
 		elog(FATAL, "could not reattach to shared memory (key=%d, addr=%p): %m",
 			 (int) UsedShmemSegID, UsedShmemSegAddr);
 	if (hdr != origUsedShmemSegAddr)
@@ -956,12 +509,6 @@
 {
 	if (UsedShmemSegAddr != NULL)
 	{
-		if ((shmdt(UsedShmemSegAddr) < 0)
-#if defined(EXEC_BACKEND) && defined(__CYGWIN__)
-		/* Work-around for cygipc exec bug */
-			&& shmdt(NULL) < 0
-#endif
-			)
 			elog(LOG, "shmdt(%p) failed: %m", UsedShmemSegAddr);
 		UsedShmemSegAddr = NULL;
 	}
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -234,7 +234,7 @@
 		}
 		*mapped_address = NULL;
 		*mapped_size = 0;
-		if (op == DSM_OP_DESTROY && shm_unlink(name) != 0)
+		if (op == DSM_OP_DESTROY)
 		{
 			ereport(elevel,
 					(errcode_for_dynamic_shared_memory(),
@@ -255,9 +255,6 @@
 	 */
 	ReserveExternalFD();
 
-	flags = O_RDWR | (op == DSM_OP_CREATE ? O_CREAT | O_EXCL : 0);
-	if ((fd = shm_open(name, flags, PG_FILE_MODE_OWNER)) == -1)
-	{
 		ReleaseExternalFD();
 		if (op == DSM_OP_ATTACH || errno != EEXIST)
 			ereport(elevel,
@@ -265,79 +262,6 @@
 					 errmsg("could not open shared memory segment \"%s\": %m",
 							name)));
 		return false;
-	}
-
-	/*
-	 * If we're attaching the segment, determine the current size; if we are
-	 * creating the segment, set the size to the requested value.
-	 */
-	if (op == DSM_OP_ATTACH)
-	{
-		struct stat st;
-
-		if (fstat(fd, &st) != 0)
-		{
-			int			save_errno;
-
-			/* Back out what's already been done. */
-			save_errno = errno;
-			close(fd);
-			ReleaseExternalFD();
-			errno = save_errno;
-
-			ereport(elevel,
-					(errcode_for_dynamic_shared_memory(),
-					 errmsg("could not stat shared memory segment \"%s\": %m",
-							name)));
-			return false;
-		}
-		request_size = st.st_size;
-	}
-	else if (dsm_impl_posix_resize(fd, request_size) != 0)
-	{
-		int			save_errno;
-
-		/* Back out what's already been done. */
-		save_errno = errno;
-		close(fd);
-		ReleaseExternalFD();
-		shm_unlink(name);
-		errno = save_errno;
-
-		ereport(elevel,
-				(errcode_for_dynamic_shared_memory(),
-				 errmsg("could not resize shared memory segment \"%s\" to %zu bytes: %m",
-						name, request_size)));
-		return false;
-	}
-
-	/* Map it. */
-	address = mmap(NULL, request_size, PROT_READ | PROT_WRITE,
-				   MAP_SHARED | MAP_HASSEMAPHORE | MAP_NOSYNC, fd, 0);
-	if (address == MAP_FAILED)
-	{
-		int			save_errno;
-
-		/* Back out what's already been done. */
-		save_errno = errno;
-		close(fd);
-		ReleaseExternalFD();
-		if (op == DSM_OP_CREATE)
-			shm_unlink(name);
-		errno = save_errno;
-
-		ereport(elevel,
-				(errcode_for_dynamic_shared_memory(),
-				 errmsg("could not map shared memory segment \"%s\": %m",
-						name)));
-		return false;
-	}
-	*mapped_address = address;
-	*mapped_size = request_size;
-	close(fd);
-	ReleaseExternalFD();
-
-	return true;
 }
 
 /*
@@ -506,8 +430,6 @@
 			segsize = request_size;
 		}
 
-		if ((ident = shmget(key, segsize, flags)) == -1)
-		{
 			if (op == DSM_OP_ATTACH || errno != EEXIST)
 			{
 				int			save_errno = errno;
@@ -521,16 +443,12 @@
 			return false;
 		}
 
-		*ident_cache = ident;
-		*impl_private = ident_cache;
-	}
-
 	/* Handle teardown cases. */
 	if (op == DSM_OP_DETACH || op == DSM_OP_DESTROY)
 	{
 		pfree(ident_cache);
 		*impl_private = NULL;
-		if (*mapped_address != NULL && shmdt(*mapped_address) != 0)
+		if (*mapped_address != NULL)
 		{
 			ereport(elevel,
 					(errcode_for_dynamic_shared_memory(),
@@ -540,7 +458,7 @@
 		}
 		*mapped_address = NULL;
 		*mapped_size = 0;
-		if (op == DSM_OP_DESTROY && shmctl(ident, IPC_RMID, NULL) < 0)
+		if (op == DSM_OP_DESTROY)
 		{
 			ereport(elevel,
 					(errcode_for_dynamic_shared_memory(),
@@ -554,41 +472,22 @@
 	/* If we're attaching it, we must use IPC_STAT to determine the size. */
 	if (op == DSM_OP_ATTACH)
 	{
-		struct shmid_ds shm;
-
-		if (shmctl(ident, IPC_STAT, &shm) != 0)
-		{
 			ereport(elevel,
 					(errcode_for_dynamic_shared_memory(),
 					 errmsg("could not stat shared memory segment \"%s\": %m",
 							name)));
 			return false;
 		}
-		request_size = shm.shm_segsz;
-	}
 
-	/* Map it. */
-	address = shmat(ident, NULL, PG_SHMAT_FLAGS);
-	if (address == (void *) -1)
-	{
-		int			save_errno;
+	int save_errno = errno;
 
 		/* Back out what's already been done. */
-		save_errno = errno;
-		if (op == DSM_OP_CREATE)
-			shmctl(ident, IPC_RMID, NULL);
 		errno = save_errno;
-
 		ereport(elevel,
 				(errcode_for_dynamic_shared_memory(),
 				 errmsg("could not map shared memory segment \"%s\": %m",
 						name)));
 		return false;
-	}
-	*mapped_address = address;
-	*mapped_size = request_size;
-
-	return true;
 }
 #endif
 
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1006,38 +1006,7 @@
 static const char *
 choose_dsm_implementation(void)
 {
-#if defined(HAVE_SHM_OPEN) && !defined(__sun__)
-	int			ntries = 10;
-	pg_prng_state prng_state;
-
-	/* Initialize prng; this function is its only user in this program. */
-	pg_prng_seed(&prng_state, (uint64) (getpid() ^ time(NULL)));
-
-	while (ntries > 0)
-	{
-		uint32		handle;
-		char		name[64];
-		int			fd;
-
-		handle = pg_prng_uint32(&prng_state);
-		snprintf(name, 64, "/PostgreSQL.%u", handle);
-		if ((fd = shm_open(name, O_CREAT | O_RDWR | O_EXCL, 0600)) != -1)
-		{
-			close(fd);
-			shm_unlink(name);
-			return "posix";
-		}
-		if (errno != EEXIST)
-			break;
-		--ntries;
-	}
-#endif
-
-#ifdef WIN32
-	return "windows";
-#else
 	return "sysv";
-#endif
 }
 
 /*