tracing: Use __this_cpu_inc/dec operation instead of __get_cpu_var

__this_cpu_inc_return() or __this_cpu_dec generates a single instruction,
which is faster than __get_cpu_var operation.

Link: http://lkml.kernel.org/r/50A9C1BD.1060308@gmail.com

Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Shan Wei <davidshan@tencent.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ca9b7dfed8ef..07888e15c694 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1344,7 +1344,7 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
          */
         preempt_disable_notrace();
 
-        use_stack = ++__get_cpu_var(ftrace_stack_reserve);
+        use_stack = __this_cpu_inc_return(ftrace_stack_reserve);
         /*
          * We don't need any atomic variables, just a barrier.
          * If an interrupt comes in, we don't care, because it would
@@ -1398,7 +1398,7 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
  out:
         /* Again, don't let gcc optimize things here */
         barrier();
-        __get_cpu_var(ftrace_stack_reserve)--;
+        __this_cpu_dec(ftrace_stack_reserve);
         preempt_enable_notrace();
 
 }