tracing: Really, this is the last update for 5.6 before my pull request!

index 481ede3eac13..3f7ee102868a 100644
@@ -5867,8 +5867,15 @@ ftrace_graph_release(struct inode *inode, struct file *file)
 
 		mutex_unlock(&graph_lock);
 
-		/* Wait till all users are no longer using the old hash */
-		synchronize_rcu();
+		/*
+		 * We need to do a hard force of sched synchronization.
+		 * This is because we use preempt_disable() to do RCU, but
+		 * the function tracers can be called where RCU is not watching
+		 * (like before user_exit()). We can not rely on the RCU
+		 * infrastructure to do the synchronization, thus we must do it
+		 * ourselves.
+		 */
+		schedule_on_each_cpu(ftrace_sync);
 
 		free_ftrace_hash(old_hash);
 	}

index 8c52f5de9384..3c75d29bd861 100644
@@ -979,6 +979,7 @@ static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
 	 * Have to open code "rcu_dereference_sched()" because the
 	 * function graph tracer can be called when RCU is not
 	 * "watching".
+	 * Protected with schedule_on_each_cpu(ftrace_sync)
 	 */
 	hash = rcu_dereference_protected(ftrace_graph_hash, !preemptible());
 

@@ -1031,6 +1032,7 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr)
 	 * Have to open code "rcu_dereference_sched()" because the
 	 * function graph tracer can be called when RCU is not
 	 * "watching".
+	 * Protected with schedule_on_each_cpu(ftrace_sync)
 	 */
 	notrace_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
 						 !preemptible());

index f174a59d3903..2de2f9f7aab9 100644
@@ -372,7 +372,7 @@ static void __init setup_boot_config(const char *cmdline)
 
 	copy = memblock_alloc(size + 1, SMP_CACHE_BYTES);
 	if (!copy) {
-		pr_err("Failed to allocate memory for boot config\n");
+		pr_err("Failed to allocate memory for bootconfig\n");
 		return;
 	}
 

@@ -380,9 +380,9 @@ static void __init setup_boot_config(const char *cmdline)
 	copy[size] = '\0';
 
 	if (xbc_init(copy) < 0)
-		pr_err("Failed to parse boot config\n");
+		pr_err("Failed to parse bootconfig\n");
 	else {
-		pr_info("Load boot config: %d bytes\n", size);
+		pr_info("Load bootconfig: %d bytes\n", size);
 		/* keys starting with "kernel." are passed via cmdline */
 		extra_command_line = xbc_make_cmdline("kernel");
 		/* Also, "init." keys are init arguments */

index 055014e233a5..a98ae136529c 100644
@@ -373,7 +373,8 @@ static struct xbc_node * __init xbc_add_sibling(char *data, u32 flag)
 				sib->next = xbc_node_index(node);
 			}
 		}
-	}
+	} else
+		xbc_parse_error("Too many nodes", data);
 
 	return node;
 }

@@ -657,8 +658,10 @@ static int __init xbc_verify_tree(void)
 	struct xbc_node *n, *m;
 
 	/* Empty tree */
-	if (xbc_node_num == 0)
+	if (xbc_node_num == 0) {
+		xbc_parse_error("Empty config", xbc_data);
 		return -ENOENT;
+	}
 
 	for (i = 0; i < xbc_node_num; i++) {
 		if (xbc_nodes[i].next > xbc_node_num) {

@@ -732,12 +735,17 @@ int __init xbc_init(char *buf)
 	char *p, *q;
 	int ret, c;
 
-	if (xbc_data)
+	if (xbc_data) {
+		pr_err("Error: bootconfig is already initialized.\n");
 		return -EBUSY;
+	}
 
 	ret = strlen(buf);
-	if (ret > XBC_DATA_MAX - 1 || ret == 0)
+	if (ret > XBC_DATA_MAX - 1 || ret == 0) {
+		pr_err("Error: Config data is %s.\n",
+			ret ? "too big" : "empty");
 		return -ERANGE;
+	}
 
 	xbc_data = buf;
 	xbc_data_size = ret + 1;

index a98ae136529c..afb2e767e6fe 100644
@@ -728,7 +728,8 @@ void __init xbc_destroy_all(void)
  *
  * This parses the boot config text in @buf. @buf must be a
  * null terminated string and smaller than XBC_DATA_MAX.
- * Return 0 if succeeded, or -errno if there is any error.
+ * Return the number of stored nodes (>0) if succeeded, or -errno
+ * if there is any error.
  */
 int __init xbc_init(char *buf)
 {

@@ -788,6 +789,8 @@ int __init xbc_init(char *buf)
 
 	if (ret < 0)
 		xbc_destroy_all();
+	else
+		ret = xbc_node_num;
 
 	return ret;
 }

index 91c9a5c0c499..47f488458328 100644
@@ -268,6 +268,7 @@ int apply_xbc(const char *path, const char *xbc_path)
 		return ret;
 	}
 	printf("Apply %s to %s\n", xbc_path, path);
+	printf("\tNumber of nodes: %d\n", ret);
 	printf("\tSize: %u bytes\n", (unsigned int)size);
 	printf("\tChecksum: %d\n", (unsigned int)csum);
 

index 2de2f9f7aab9..491f1cdb3105 100644
@@ -342,6 +342,7 @@ static void __init setup_boot_config(const char *cmdline)
 	char *data, *copy;
 	const char *p;
 	u32 *hdr;
+	int ret;
 
 	p = strstr(cmdline, "bootconfig");
 	if (!p || (p != cmdline && !isspace(*(p-1))) ||

@@ -379,10 +380,11 @@ static void __init setup_boot_config(const char *cmdline)
 	memcpy(copy, data, size);
 	copy[size] = '\0';
 
-	if (xbc_init(copy) < 0)
+	ret = xbc_init(copy);
+	if (ret < 0)
 		pr_err("Failed to parse bootconfig\n");
 	else {
-		pr_info("Load bootconfig: %d bytes\n", size);
+		pr_info("Load bootconfig: %d bytes %d nodes\n", size, ret);
 		/* keys starting with "kernel." are passed via cmdline */
 		extra_command_line = xbc_make_cmdline("kernel");
 		/* Also, "init." keys are init arguments */