Avoid a memory allocation in the backend startup code, to avoid having to check

alvherre · alvherre · commit a1e1ef4f7764 · 2009-05-04T02:24:17.000Z
whether it failed.  Modelled after catcache.c's usage of DlList, per suggestion
from Tom.
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.578 2009/05/02 22:02:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.579 2009/05/04 02:24:17 alvherre Exp $
  *
  * NOTES
  *
@@ -143,6 +143,7 @@ typedef struct bkend
 	long		cancel_key;		/* cancel key for cancels for this backend */
 	bool		is_autovacuum;	/* is it an autovacuum process? */
 	bool		dead_end;		/* is it going to send an error and quit? */
+	Dlelem		elem;			/* self pointer into BackendList */
 } Backend;
 
 static Dllist *BackendList;
@@ -2459,7 +2460,6 @@ CleanupBackend(int pid,
 #endif
 			DLRemove(curr);
 			free(bp);
-			DLFreeElem(curr);
 			break;
 		}
 	}
@@ -2506,7 +2506,6 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 #endif
 			DLRemove(curr);
 			free(bp);
-			DLFreeElem(curr);
 			/* Keep looping so we can signal remaining backends */
 		}
 		else
@@ -3014,7 +3013,8 @@ BackendStartup(Port *port)
 	bn->is_autovacuum = false;
 	bn->dead_end = (port->canAcceptConnections != CAC_OK &&
 					port->canAcceptConnections != CAC_WAITBACKUP);
-	DLAddHead(BackendList, DLNewElem(bn));
+	DLInitElem(&bn->elem, bn);
+	DLAddHead(BackendList, &bn->elem);
 #ifdef EXEC_BACKEND
 	if (!bn->dead_end)
 		ShmemBackendArrayAdd(bn);

Original file line number	Diff line number	Diff line change
`@@ -37,7 +37,7 @@`
`37`	`37`	`*`
`38`	`38`	`*`
`39`	`39`	`* IDENTIFICATION`
`40`		`- * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.578 2009/05/02 22:02:37 tgl Exp $`
	`40`	`+ * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.579 2009/05/04 02:24:17 alvherre Exp $`
`41`	`41`	`*`
`42`	`42`	`* NOTES`
`43`	`43`	`*`
`@@ -143,6 +143,7 @@ typedef struct bkend`
`143`	`143`	`long cancel_key; /* cancel key for cancels for this backend */`
`144`	`144`	`bool is_autovacuum; /* is it an autovacuum process? */`
`145`	`145`	`bool dead_end; /* is it going to send an error and quit? */`
	`146`	`+ Dlelem elem; /* self pointer into BackendList */`
`146`	`147`	`} Backend;`
`147`	`148`
`148`	`149`	`static Dllist *BackendList;`
`@@ -2459,7 +2460,6 @@ CleanupBackend(int pid,`
`2459`	`2460`	`#endif`
`2460`	`2461`	`DLRemove(curr);`
`2461`	`2462`	`free(bp);`
`2462`		`- DLFreeElem(curr);`
`2463`	`2463`	`break;`
`2464`	`2464`	`}`
`2465`	`2465`	`}`
`@@ -2506,7 +2506,6 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)`
`2506`	`2506`	`#endif`
`2507`	`2507`	`DLRemove(curr);`
`2508`	`2508`	`free(bp);`
`2509`		`- DLFreeElem(curr);`
`2510`	`2509`	`/* Keep looping so we can signal remaining backends */`
`2511`	`2510`	`}`
`2512`	`2511`	`else`
`@@ -3014,7 +3013,8 @@ BackendStartup(Port *port)`
`3014`	`3013`	`bn->is_autovacuum = false;`
`3015`	`3014`	`bn->dead_end = (port->canAcceptConnections != CAC_OK &&`
`3016`	`3015`	`port->canAcceptConnections != CAC_WAITBACKUP);`
`3017`		`- DLAddHead(BackendList, DLNewElem(bn));`
	`3016`	`+ DLInitElem(&bn->elem, bn);`
	`3017`	`+ DLAddHead(BackendList, &bn->elem);`
`3018`	`3018`	`#ifdef EXEC_BACKEND`
`3019`	`3019`	`if (!bn->dead_end)`
`3020`	`3020`	`ShmemBackendArrayAdd(bn);`