7 files changed, 69 insertions, 7 deletions
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 756a9d07fb0..7e92e898460 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -3619,17 +3619,20 @@ INJECTION_POINT(name);
     </para>
 
     <para>
-     An injection point with a given <literal>name</literal> can be loaded
-     using macro:
+     Executing an injection point can require allocating a small amount of
+     memory, which can fail. If you need to have an injection point in a
+     critical section where dynamic allocations are not allowed, you can use
+     a two-step approach with the following macros:
 <programlisting>
 INJECTION_POINT_LOAD(name);
+INJECTION_POINT_CACHED(name);
 </programlisting>
 
-     This will load the injection point callback into the process cache,
-     doing all memory allocations at this stage without running the callback.
-     This is useful when an injection point is attached in a critical section
-     where no memory can be allocated: load the injection point outside the
-     critical section, then run it in the critical section.
+     Before entering the critical section,
+     call <function>INJECTION_POINT_LOAD</function>. It checks the shared
+     memory state, and loads the callback into backend-private memory if it is
+     active. Inside the critical section, use
+     <function>INJECTION_POINT_CACHED</function> to execute the callback.
     </para>
 
     <para>
diff --git a/src/backend/utils/misc/injection_point.c b/src/backend/utils/misc/injection_point.c
index 84ad5e470d7..8ad0c27bc8a 100644
--- a/src/backend/utils/misc/injection_point.c
+++ b/src/backend/utils/misc/injection_point.c
@@ -553,3 +553,20 @@ InjectionPointRun(const char *name)
 	elog(ERROR, "Injection points are not supported by this build");
 #endif
 }
+
+/*
+ * Execute an injection point directly from the cache, if defined.
+ */
+void
+InjectionPointCached(const char *name)
+{
+#ifdef USE_INJECTION_POINTS
+	InjectionPointCacheEntry *cache_entry;
+
+	cache_entry = injection_point_cache_get(name);
+	if (cache_entry)
+		cache_entry->callback(name, cache_entry->private_data);
+#else
+	elog(ERROR, "Injection points are not supported by this build");
+#endif
+}
diff --git a/src/include/utils/injection_point.h b/src/include/utils/injection_point.h
index bd3a62425c3..a385e3df649 100644
--- a/src/include/utils/injection_point.h
+++ b/src/include/utils/injection_point.h
@@ -17,9 +17,11 @@
 #ifdef USE_INJECTION_POINTS
 #define INJECTION_POINT_LOAD(name) InjectionPointLoad(name)
 #define INJECTION_POINT(name) InjectionPointRun(name)
+#define INJECTION_POINT_CACHED(name) InjectionPointCached(name)
 #else
 #define INJECTION_POINT_LOAD(name) ((void) name)
 #define INJECTION_POINT(name) ((void) name)
+#define INJECTION_POINT_CACHED(name) ((void) name)
 #endif
 
 /*
@@ -38,6 +40,7 @@ extern void InjectionPointAttach(const char *name,
 								 int private_data_size);
 extern void InjectionPointLoad(const char *name);
 extern void InjectionPointRun(const char *name);
+extern void InjectionPointCached(const char *name);
 extern bool InjectionPointDetach(const char *name);
 
 #endif							/* INJECTION_POINT_H */
diff --git a/src/test/modules/injection_points/expected/injection_points.out b/src/test/modules/injection_points/expected/injection_points.out
index 2f60da900bb..f25bbe4966e 100644
--- a/src/test/modules/injection_points/expected/injection_points.out
+++ b/src/test/modules/injection_points/expected/injection_points.out
@@ -129,6 +129,12 @@ SELECT injection_points_detach('TestInjectionLog2');
 (1 row)
 
 -- Loading
+SELECT injection_points_cached('TestInjectionLogLoad'); -- nothing in cache
+ injection_points_cached 
+-------------------------
+ 
+(1 row)
+
 SELECT injection_points_load('TestInjectionLogLoad'); -- nothing
  injection_points_load 
 -----------------------
@@ -147,6 +153,13 @@ SELECT injection_points_load('TestInjectionLogLoad'); -- nothing happens
  
 (1 row)
 
+SELECT injection_points_cached('TestInjectionLogLoad'); -- runs from cache
+NOTICE:  notice triggered for injection point TestInjectionLogLoad
+ injection_points_cached 
+-------------------------
+ 
+(1 row)
+
 SELECT injection_points_run('TestInjectionLogLoad'); -- runs from cache
 NOTICE:  notice triggered for injection point TestInjectionLogLoad
  injection_points_run 
diff --git a/src/test/modules/injection_points/injection_points--1.0.sql b/src/test/modules/injection_points/injection_points--1.0.sql
index e275c2cf5b6..0f280419a55 100644
--- a/src/test/modules/injection_points/injection_points--1.0.sql
+++ b/src/test/modules/injection_points/injection_points--1.0.sql
@@ -35,6 +35,16 @@ AS 'MODULE_PATHNAME', 'injection_points_run'
 LANGUAGE C STRICT PARALLEL UNSAFE;
 
 --
+-- injection_points_cached()
+--
+-- Executes the action attached to the injection point, from local cache.
+--
+CREATE FUNCTION injection_points_cached(IN point_name TEXT)
+RETURNS void
+AS 'MODULE_PATHNAME', 'injection_points_cached'
+LANGUAGE C STRICT PARALLEL UNSAFE;
+
+--
 -- injection_points_wakeup()
 --
 -- Wakes up a waiting injection point.
diff --git a/src/test/modules/injection_points/injection_points.c b/src/test/modules/injection_points/injection_points.c
index b6c8e893246..15f9d0233c3 100644
--- a/src/test/modules/injection_points/injection_points.c
+++ b/src/test/modules/injection_points/injection_points.c
@@ -334,6 +334,20 @@ injection_points_run(PG_FUNCTION_ARGS)
 }
 
 /*
+ * SQL function for triggering an injection point from cache.
+ */
+PG_FUNCTION_INFO_V1(injection_points_cached);
+Datum
+injection_points_cached(PG_FUNCTION_ARGS)
+{
+	char	   *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
+
+	INJECTION_POINT_CACHED(name);
+
+	PG_RETURN_VOID();
+}
+
+/*
  * SQL function for waking up an injection point waiting in injection_wait().
  */
 PG_FUNCTION_INFO_V1(injection_points_wakeup);
diff --git a/src/test/modules/injection_points/sql/injection_points.sql b/src/test/modules/injection_points/sql/injection_points.sql
index fabf0a8823b..e3a481d6044 100644
--- a/src/test/modules/injection_points/sql/injection_points.sql
+++ b/src/test/modules/injection_points/sql/injection_points.sql
@@ -42,9 +42,11 @@ SELECT injection_points_run('TestInjectionLog2'); -- notice
 SELECT injection_points_detach('TestInjectionLog2');
 
 -- Loading
+SELECT injection_points_cached('TestInjectionLogLoad'); -- nothing in cache
 SELECT injection_points_load('TestInjectionLogLoad'); -- nothing
 SELECT injection_points_attach('TestInjectionLogLoad', 'notice');
 SELECT injection_points_load('TestInjectionLogLoad'); -- nothing happens
+SELECT injection_points_cached('TestInjectionLogLoad'); -- runs from cache
 SELECT injection_points_run('TestInjectionLogLoad'); -- runs from cache
 SELECT injection_points_detach('TestInjectionLogLoad');