ftrace: Clean up the recursion code a bit

In trace_test_and_set_recursion(), current->trace_recursion is placed into a
variable, and that variable should be used for the processing, as there's no
reason to dereference current multiple times.

On trace_clear_recursion(), current->trace_recursion is modified and there's
no reason to copy it over to a variable.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index 228cc56ed66ee638309505aec882cffbb184a639..a9f9c5714e6505882b19000f6d44f1e705e3daef 100644 (file)
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -162,7 +162,7 @@ extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
 static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
                                                        int start, int max)
 {
-       unsigned int val = current->trace_recursion;
+       unsigned int val = READ_ONCE(current->trace_recursion);
        int bit;
 
        /* A previous recursion check was made */
@@ -176,18 +176,15 @@ static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsign
                 * a switch between contexts. Allow for a single recursion.
                 */
                bit = TRACE_TRANSITION_BIT;
-               if (trace_recursion_test(bit)) {
+               if (val & (1 << bit)) {
                        do_ftrace_record_recursion(ip, pip);
                        return -1;
                }
-               trace_recursion_set(bit);
-               barrier();
-               return bit + 1;
+       } else {
+               /* Normal check passed, clear the transition to allow it again */
+               val &= ~(1 << TRACE_TRANSITION_BIT);
        }
 
-       /* Normal check passed, clear the transition to allow it again */
-       trace_recursion_clear(TRACE_TRANSITION_BIT);
-
        val |= 1 << bit;
        current->trace_recursion = val;
        barrier();
@@ -197,17 +194,12 @@ static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsign
 
 static __always_inline void trace_clear_recursion(int bit)
 {
-       unsigned int val = current->trace_recursion;
-
        if (!bit)
                return;
 
-       bit--;
-       bit = 1 << bit;
-       val &= ~bit;
-
        barrier();
-       current->trace_recursion = val;
+       bit--;
+       trace_recursion_clear(bit);
 }
 
 /**