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/20200201072703.17330-1-frextrite@gmail.com
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0e9612c309956c00b379273250ea5e61cdd17392..01d2ecd661618fdb7d83600d7b8cd990d00d8405 100644 (file)
--- 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
index f5480a2aa334cb70845d61e87a06b1aaf6999ba0..18ceab59a5bae9e23d6acce3c5622b930e2b69f8 100644 (file)
--- 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