Limit depth of forced recursion for CLOBBER_CACHE_RECURSIVELY.

tglsfdc · tglsfdc · commit 90fd3bfd1707 · 2018-09-07T18:13:58.000-04:00
It's somewhat surprising that we got away with this before. (Actually, since nobody tests this routinely AFAIK, it might've been broken for awhile. But it's definitely broken in the wake of commit f868a81.) It seems sufficient to limit the forced recursion to a small number of levels. Back-patch to all supported branches, like the preceding patch. Discussion: https://postgr.es/m/12259.1532117714@sss.pgh.pa.us
diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
@@ -708,7 +708,17 @@ AcceptInvalidationMessages(void)
 		}
 	}
 #elif defined(CLOBBER_CACHE_RECURSIVELY)
-	InvalidateSystemCaches();
+	{
+		static int	recursion_depth = 0;
+
+		/* Maximum depth is arbitrary depending on your threshold of pain */
+		if (recursion_depth < 3)
+		{
+			recursion_depth++;
+			InvalidateSystemCaches();
+			recursion_depth--;
+		}
+	}
 #endif
 }
 

Original file line number	Diff line number	Diff line change
`@@ -708,7 +708,17 @@ AcceptInvalidationMessages(void)`
`708`	`708`	`}`
`709`	`709`	`}`
`710`	`710`	`#elif defined(CLOBBER_CACHE_RECURSIVELY)`
`711`		`- InvalidateSystemCaches();`
	`711`	`+ {`
	`712`	`+ static int recursion_depth = 0;`
	`713`	`+`
	`714`	`+ /* Maximum depth is arbitrary depending on your threshold of pain */`
	`715`	`+ if (recursion_depth < 3)`
	`716`	`+ {`
	`717`	`+ recursion_depth++;`
	`718`	`+ InvalidateSystemCaches();`
	`719`	`+ recursion_depth--;`
	`720`	`+ }`
	`721`	`+ }`
`712`	`722`	`#endif`
`713`	`723`	`}`
`714`	`724`