tracing: Annotate ftrace_graph_hash pointer with __rcu

Fix following instances of sparse error kernel/trace/ftrace.c:5664:29: error: incompatible types in comparison kernel/trace/ftrace.c:5785:21: error: incompatible types in comparison kernel/trace/ftrace.c:5864:36: error: incompatible types in comparison kernel/trace/ftrace.c:5866:25: error: incompatible types in comparison Use rcu_dereference_protected to access the __rcu annotated pointer. Link: http://lkml.kernel.org/r/[email protected] Reviewed-by: Joel Fernandes (Google) <[email protected]> Signed-off-by: Amol Grover <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]>
ambv · Feb 5, 2020 · 24a9729 · 24a9729
1 parent 7495e09
commit 24a9729
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Showing 2 changed files with 7 additions and 4 deletions.
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
@@ -5591,7 +5591,7 @@ static const struct file_operations ftrace_notrace_fops = {
 
 static DEFINE_MUTEX(graph_lock);
 
-struct ftrace_hash *ftrace_graph_hash = EMPTY_HASH;
+struct ftrace_hash __rcu *ftrace_graph_hash = EMPTY_HASH;
 struct ftrace_hash *ftrace_graph_notrace_hash = EMPTY_HASH;
 
 enum graph_filter_type {

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
@@ -964,22 +964,25 @@ extern void __trace_graph_return(struct trace_array *tr,
 				 unsigned long flags, int pc);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
-extern struct ftrace_hash *ftrace_graph_hash;
+extern struct ftrace_hash __rcu *ftrace_graph_hash;
 extern struct ftrace_hash *ftrace_graph_notrace_hash;
 
 static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
 {
 	unsigned long addr = trace->func;
 	int ret = 0;
+	struct ftrace_hash *hash;
 
 	preempt_disable_notrace();
 
-	if (ftrace_hash_empty(ftrace_graph_hash)) {
+	hash = rcu_dereference_protected(ftrace_graph_hash, !preemptible());
+
+	if (ftrace_hash_empty(hash)) {
 		ret = 1;
 		goto out;
 	}
 
-	if (ftrace_lookup_ip(ftrace_graph_hash, addr)) {
+	if (ftrace_lookup_ip(hash, addr)) {
 
 		/*
 		 * This needs to be cleared on the return functions