ring-buffer: Remove duplicate use of '&' in recursive code

A clean up of the recursive protection code changed

  val = this_cpu_read(current_context);
  val--;
  val &= this_cpu_read(current_context);

to

  val = this_cpu_read(current_context);
  val &= val & (val - 1);

Which has a duplicate use of '&' as the above is the same as

  val = val & (val - 1);

Actually, it would be best to remove that line altogether and
just add it to where it is used.

And Christoph even mentioned that it can be further compacted to
just a single line:

  __this_cpu_and(current_context, __this_cpu_read(current_context) - 1);

Link: http://lkml.kernel.org/alpine.DEB.2.11.1503271423580.23114@gentwo.org
Suggested-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 922048a0f7eab0f33229cb2c129948f68f4a1074..0315d43176d80d264c37f22ba403a5089a124c48 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2703,10 +2703,7 @@ static __always_inline int trace_recursive_lock(void)
 
 static __always_inline void trace_recursive_unlock(void)
 {
-       unsigned int val = __this_cpu_read(current_context);
-
-       val &= val & (val - 1);
-       __this_cpu_write(current_context, val);
+       __this_cpu_and(current_context, __this_cpu_read(current_context) - 1);
 }
 
 #else