Index: main/manager.c
===================================================================
--- main/manager.c	(revision 173354)
+++ main/manager.c	(working copy)
@@ -173,6 +173,9 @@
 	struct eventqent *last_ev;	/*!< last event processed. */
 	int writetimeout;	/*!< Timeout for ast_carefulwrite() */
 	int pending_event;         /*!< Pending events indicator in case when waiting_thread is NULL */
+	/* http-specific variables */
+	ast_cond_t file_condition;
+	unsigned int file_ready:1;
 	AST_LIST_ENTRY(mansession) list;
 };
 
@@ -3551,6 +3554,8 @@
 		AST_LIST_INSERT_HEAD(&sessions, s, list);
 		ast_atomic_fetchadd_int(&num_sessions, 1);
 		AST_LIST_UNLOCK(&sessions);
+		ast_cond_init(&s->file_condition, NULL);
+		s->file_ready = 1;
 	}
 
 	ast_mutex_unlock(&s->__lock);
@@ -3560,9 +3565,15 @@
 		goto generic_callback_out;
 	}
 
+	ast_mutex_lock(&s->__lock);
+	if (!s->file_ready) {
+		ast_cond_wait(&s->file_condition, &s->__lock);
+	}
 	s->fd = mkstemp(template);	/* create a temporary file for command output */
 	unlink(template);
 	s->f = fdopen(s->fd, "w+");
+	s->file_ready = 0;
+	ast_mutex_unlock(&s->__lock);
 
 	for (x = 0, v = params; v && (x < AST_MAX_MANHEADERS); x++, v = v->next) {
 		hdrlen = strlen(v->name) + strlen(v->value) + 3;
@@ -3608,6 +3619,7 @@
 		ast_str_append(&out, 0, ROW_FMT, TEST_STRING);
 	}
 
+	/* I should expect that this should never be NULL */
 	if (s->f != NULL) {	/* have temporary output */
 		char *buf;
 		size_t l = ftell(s->f);
@@ -3623,9 +3635,13 @@
 		} else if (format == FORMAT_XML || format == FORMAT_HTML) {
 			xml_translate(&out, "", params, format);
 		}
+		ast_mutex_lock(&s->__lock);
 		fclose(s->f);
 		s->f = NULL;
 		s->fd = -1;
+		s->file_ready = 1;
+		ast_cond_signal(&s->file_condition);
+		ast_mutex_unlock(&s->__lock);
 	}
 
 	if (format == FORMAT_XML) {