parisc/ftrace: use static key to enable/disable function graph tracer

This avoids using dereference_function_descriptor in the ftrace code
path, and it's also faster.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
index 3a577186f71b45ae54cf6f5b7f7b5f7c4a61ef0e..2a1f826b3defdcc71a31dae4cd5ee6071449b90a 100644 (file)
--- a/arch/parisc/kernel/ftrace.c
+++ b/arch/parisc/kernel/ftrace.c
@@ -15,6 +15,7 @@
 #include <linux/uaccess.h>
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>
+#include <linux/jump_label.h>
 
 #include <asm/assembly.h>
 #include <asm/sections.h>
@@ -24,6 +25,8 @@
 #define __hot __section(".text.hot")
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static DEFINE_STATIC_KEY_FALSE(ftrace_graph_enable);
+
 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
@@ -60,9 +63,7 @@ void notrace __hot ftrace_function_trampoline(unsigned long parent,
        ftrace_func(self_addr, parent, function_trace_op, fregs);
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-       if (dereference_function_descriptor(ftrace_graph_return) !=
-           dereference_function_descriptor(ftrace_stub) ||
-           ftrace_graph_entry != ftrace_graph_entry_stub) {
+       if (static_branch_unlikely(&ftrace_graph_enable)) {
                unsigned long *parent_rp;
 
                /* calculate pointer to %rp in stack */
@@ -80,11 +81,13 @@ void notrace __hot ftrace_function_trampoline(unsigned long parent,
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 int ftrace_enable_ftrace_graph_caller(void)
 {
+       static_key_enable(&ftrace_graph_enable.key);
        return 0;
 }
 
 int ftrace_disable_ftrace_graph_caller(void)
 {
+       static_key_enable(&ftrace_graph_enable.key);
        return 0;
 }
 #endif