Refactor EXEC_BACKEND code so that postmaster child processes reattach

to shared memory as soon as possible, ie, right after read_backend_variables.
The effective difference from the original code is that this happens
before instead of after read_nondefault_variables(), which loads GUC
information and is apparently capable of expanding the backend's memory
allocation more than you'd think it should.  This should fix the
failure-to-attach-to-shared-memory reports we've been seeing on Windows.
Also clean up a few bits of unnecessarily grotty EXEC_BACKEND code.

src/backend/storage/file/fd.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.113 2004/09/16 16:58:32 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.114 2004/12/29 21:36:05 tgl Exp $
  *
  * NOTES:
  *
@@ -228,6 +228,7 @@ static File fileNameOpenFile(FileName fileName, int fileFlags, int fileMode);
 static char *filepath(const char *filename);
 static void AtProcExit_Files(int code, Datum arg);
 static void CleanupTempFiles(bool isProcExit);
+static void RemovePgTempFilesInDir(const char *tmpdirname);
 
 
 /*
@@ -1482,59 +1483,83 @@ RemovePgTempFiles(void)
 {
 	char		db_path[MAXPGPATH];
 	char		temp_path[MAXPGPATH];
-	char		rm_path[MAXPGPATH];
 	DIR		   *db_dir;
-	DIR		   *temp_dir;
 	struct dirent *db_de;
-	struct dirent *temp_de;
 
 	/*
-	 * Cycle through pg_tempfiles for all databases and remove old temp
-	 * files.
+	 * Cycle through pgsql_tmp directories for all databases and remove old
+	 * temp files.
 	 */
 	snprintf(db_path, sizeof(db_path), "%s/base", DataDir);
-	if ((db_dir = AllocateDir(db_path)) != NULL)
+	db_dir = AllocateDir(db_path);
+	if (db_dir == NULL)
 	{
-		while ((db_de = readdir(db_dir)) != NULL)
-		{
-			if (strcmp(db_de->d_name, ".") == 0
-#ifndef EXEC_BACKEND
-			/* no PG_TEMP_FILES_DIR in DataDir in non EXEC_BACKEND case */
-				|| strcmp(db_de->d_name, "..") == 0
-#endif
-				)
-				continue;
-
-			snprintf(temp_path, sizeof(temp_path),
-					 "%s/%s/%s",
-					 db_path, db_de->d_name,
-					 PG_TEMP_FILES_DIR);
-			if ((temp_dir = AllocateDir(temp_path)) != NULL)
-			{
-				while ((temp_de = readdir(temp_dir)) != NULL)
-				{
-					if (strcmp(temp_de->d_name, ".") == 0 ||
-						strcmp(temp_de->d_name, "..") == 0)
-						continue;
-
-					snprintf(rm_path, sizeof(temp_path),
-							 "%s/%s/%s/%s",
-							 db_path, db_de->d_name,
-							 PG_TEMP_FILES_DIR,
-							 temp_de->d_name);
-
-					if (strncmp(temp_de->d_name,
-								PG_TEMP_FILE_PREFIX,
-								strlen(PG_TEMP_FILE_PREFIX)) == 0)
-						unlink(rm_path);
-					else
-						elog(LOG,
-							 "unexpected file found in temporary-files directory: \"%s\"",
-							 rm_path);
-				}
-				FreeDir(temp_dir);
-			}
-		}
-		FreeDir(db_dir);
+		/* this really should not happen */
+		elog(LOG, "could not open directory \"%s\": %m", db_path);
+		return;
 	}
+
+	while ((db_de = readdir(db_dir)) != NULL)
+	{
+		if (strcmp(db_de->d_name, ".") == 0 ||
+			strcmp(db_de->d_name, "..") == 0)
+			continue;
+
+		snprintf(temp_path, sizeof(temp_path), "%s/%s/%s",
+				 db_path, db_de->d_name, PG_TEMP_FILES_DIR);
+		RemovePgTempFilesInDir(temp_path);
+	}
+
+	FreeDir(db_dir);
+
+	/*
+	 * In EXEC_BACKEND case there is a pgsql_tmp directory at the top
+	 * level of DataDir as well.
+	 */
+#ifdef EXEC_BACKEND
+	snprintf(temp_path, sizeof(temp_path), "%s/%s",
+			 DataDir, PG_TEMP_FILES_DIR);
+	RemovePgTempFilesInDir(temp_path);
+#endif
+}
+
+/* Process one pgsql_tmp directory for RemovePgTempFiles */
+static void
+RemovePgTempFilesInDir(const char *tmpdirname)
+{
+	DIR		   *temp_dir;
+	struct dirent *temp_de;
+	char		rm_path[MAXPGPATH];
+
+	temp_dir = AllocateDir(tmpdirname);
+	if (temp_dir == NULL)
+	{
+		/* anything except ENOENT is fishy */
+		if (errno != ENOENT)
+			elog(LOG,
+				 "could not open temporary-files directory \"%s\": %m",
+				 tmpdirname);
+		return;
+	}
+
+	while ((temp_de = readdir(temp_dir)) != NULL)
+	{
+		if (strcmp(temp_de->d_name, ".") == 0 ||
+			strcmp(temp_de->d_name, "..") == 0)
+			continue;
+
+		snprintf(rm_path, sizeof(rm_path), "%s/%s",
+				 tmpdirname, temp_de->d_name);
+
+		if (strncmp(temp_de->d_name,
+					PG_TEMP_FILE_PREFIX,
+					strlen(PG_TEMP_FILE_PREFIX)) == 0)
+			unlink(rm_path);	/* note we ignore any error */
+		else
+			elog(LOG,
+				 "unexpected file found in temporary-files directory: \"%s\"",
+				 rm_path);
+	}
+
+	FreeDir(temp_dir);
 }

src/backend/storage/ipc/ipci.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.72 2004/09/29 15:15:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.73 2004/12/29 21:36:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,6 +19,7 @@
 #include "access/xlog.h"
 #include "miscadmin.h"
 #include "postmaster/bgwriter.h"
+#include "postmaster/postmaster.h"
 #include "storage/bufmgr.h"
 #include "storage/freespace.h"
 #include "storage/ipc.h"
@@ -37,14 +38,15 @@
  *		Creates and initializes shared memory and semaphores.
  *
  * This is called by the postmaster or by a standalone backend.
- * It is also called by a backend forked from the postmaster under
- * the EXEC_BACKEND case.  (In the non EXEC_BACKEND case, backends
- * start life already attached to shared memory.)  The initialization
- * functions are set up to simply "attach" to pre-existing shared memory
- * structures in the latter case.  We have to do that in order to
- * initialize pointers in local memory that reference the shared structures.
- * (In the non EXEC_BACKEND case, these pointer values are inherited via
- * fork() from the postmaster.)
+ * It is also called by a backend forked from the postmaster in the
+ * EXEC_BACKEND case.  In the latter case, the shared memory segment
+ * already exists and has been physically attached to, but we have to
+ * initialize pointers in local memory that reference the shared structures,
+ * because we didn't inherit the correct pointer values from the postmaster
+ * as we do in the fork() scenario.  The easiest way to do that is to run
+ * through the same code as before.  (Note that the called routines mostly
+ * check IsUnderPostmaster, rather than EXEC_BACKEND, to detect this case.
+ * This is a bit code-wasteful and could be cleaned up.)
  *
  * If "makePrivate" is true then we only need private memory, not shared
  * memory.	This is true for a standalone backend, false for a postmaster.
@@ -101,14 +103,16 @@ CreateSharedMemoryAndSemaphores(bool makePrivate,
 	else
 	{
 		/*
-		 * Attach to the shmem segment. (this should only ever be reached
-		 * by EXEC_BACKEND code, and only then with makePrivate == false)
+		 * We are reattaching to an existing shared memory segment.
+		 * This should only be reached in the EXEC_BACKEND case, and
+		 * even then only with makePrivate == false.
 		 */
 #ifdef EXEC_BACKEND
 		Assert(!makePrivate);
-		seghdr = PGSharedMemoryCreate(-1, makePrivate, 0);
+		Assert(UsedShmemSegAddr != NULL);
+		seghdr = UsedShmemSegAddr;
 #else
-		Assert(false);
+		elog(PANIC, "should be attached to shared memory already");
 #endif
 	}