[for-next][PATCH 2/4] tracing: Annotate ftrace_graph_hash pointer with __rcu

From: Steven Rostedt
Date: Wed Feb 05 2020 - 05:51:22 EST


From: Amol Grover <frextrite@xxxxxxxxx>

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@xxxxxxxxx

Signed-off-by: Amol Grover <frextrite@xxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
kernel/trace/ftrace.c | 2 +-
kernel/trace/trace.h | 9 ++++++---
2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0e9612c30995..01d2ecd66161 100644
--- 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 f5480a2aa334..18ceab59a5ba 100644
--- 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
--
2.24.1