diff --git a/run-command.c b/run-command.c
index 863dad52f1913d8fa20fccd23fc527580c6fcaf7..c72601056cf5ae7be2593ae89af4effc26a1b043 100644
--- a/run-command.c
+++ b/run-command.c
@@ -902,35 +902,18 @@ struct parallel_processes {
 	struct strbuf buffered_output; /* of finished children */
 };
 
-static int default_start_failure(struct child_process *cp,
-				 struct strbuf *err,
+static int default_start_failure(struct strbuf *err,
 				 void *pp_cb,
 				 void *pp_task_cb)
 {
-	int i;
-
-	strbuf_addstr(err, "Starting a child failed:");
-	for (i = 0; cp->argv[i]; i++)
-		strbuf_addf(err, " %s", cp->argv[i]);
-
 	return 0;
 }
 
 static int default_task_finished(int result,
-				 struct child_process *cp,
 				 struct strbuf *err,
 				 void *pp_cb,
 				 void *pp_task_cb)
 {
-	int i;
-
-	if (!result)
-		return 0;
-
-	strbuf_addf(err, "A child failed with return code %d:", result);
-	for (i = 0; cp->argv[i]; i++)
-		strbuf_addf(err, " %s", cp->argv[i]);
-
 	return 0;
 }
 
@@ -1048,8 +1031,7 @@ static int pp_start_one(struct parallel_processes *pp)
 	pp->children[i].process.no_stdin = 1;
 
 	if (start_command(&pp->children[i].process)) {
-		code = pp->start_failure(&pp->children[i].process,
-					 &pp->children[i].err,
+		code = pp->start_failure(&pp->children[i].err,
 					 pp->data,
 					 &pp->children[i].data);
 		strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
@@ -1117,7 +1099,7 @@ static int pp_collect_finished(struct parallel_processes *pp)
 
 		code = finish_command(&pp->children[i].process);
 
-		code = pp->task_finished(code, &pp->children[i].process,
+		code = pp->task_finished(code,
 					 &pp->children[i].err, pp->data,
 					 &pp->children[i].data);
 
diff --git a/run-command.h b/run-command.h
index 42917e8618ea469ff56d52704794b6e3bc86cf97..3d1e59e26e33d062a10698fc139f7fc0f4ae14ec 100644
--- a/run-command.h
+++ b/run-command.h
@@ -159,8 +159,7 @@ typedef int (*get_next_task_fn)(struct child_process *cp,
  * To send a signal to other child processes for abortion, return
  * the negative signal number.
  */
-typedef int (*start_failure_fn)(struct child_process *cp,
-				struct strbuf *err,
+typedef int (*start_failure_fn)(struct strbuf *err,
 				void *pp_cb,
 				void *pp_task_cb);
 
@@ -179,7 +178,6 @@ typedef int (*start_failure_fn)(struct child_process *cp,
  * the negative signal number.
  */
 typedef int (*task_finished_fn)(int result,
-				struct child_process *cp,
 				struct strbuf *err,
 				void *pp_cb,
 				void *pp_task_cb);
@@ -193,9 +191,8 @@ typedef int (*task_finished_fn)(int result,
  * (both stdout and stderr) is routed to stderr in a manner that output
  * from different tasks does not interleave.
  *
- * If start_failure_fn or task_finished_fn are NULL, default handlers
- * will be used. The default handlers will print an error message on
- * error without issuing an emergency stop.
+ * start_failure_fn and task_finished_fn can be NULL to omit any
+ * special handling.
  */
 int run_processes_parallel(int n,
 			   get_next_task_fn,
diff --git a/submodule.c b/submodule.c
index 24fb81ac62e2161e79cbd5ab1f2a241663c2a3a1..62c4356c50d4a41381336559f4e9af27e520ad0d 100644
--- a/submodule.c
+++ b/submodule.c
@@ -705,8 +705,7 @@ static int get_next_submodule(struct child_process *cp,
 	return 0;
 }
 
-static int fetch_start_failure(struct child_process *cp,
-			       struct strbuf *err,
+static int fetch_start_failure(struct strbuf *err,
 			       void *cb, void *task_cb)
 {
 	struct submodule_parallel_fetch *spf = cb;
@@ -716,8 +715,8 @@ static int fetch_start_failure(struct child_process *cp,
 	return 0;
 }
 
-static int fetch_finish(int retvalue, struct child_process *cp,
-			struct strbuf *err, void *cb, void *task_cb)
+static int fetch_finish(int retvalue, struct strbuf *err,
+			void *cb, void *task_cb)
 {
 	struct submodule_parallel_fetch *spf = cb;
 
diff --git a/test-run-command.c b/test-run-command.c
index fbe0a27ef3295fe3312fb72a478571bfb450cb25..30a64a98dc8b53a3a2d7edfaa57a8ee51d5d63e7 100644
--- a/test-run-command.c
+++ b/test-run-command.c
@@ -41,7 +41,6 @@ static int no_job(struct child_process *cp,
 }
 
 static int task_finished(int result,
-			 struct child_process *cp,
 			 struct strbuf *err,
 			 void *pp_cb,
 			 void *pp_task_cb)