tracing: Avoid unnecessary multiple recursion checks

When function tracing occurs, the following steps are made:
  If arch does not support a ftrace feature:
   call internal function (uses INTERNAL bits) which calls...
  If callback is registered to the "global" list, the list
   function is called and recursion checks the GLOBAL bits.
   then this function calls...
  The function callback, which can use the FTRACE bits to
   check for recursion.

Now if the arch does not suppport a feature, and it calls
the global list function which calls the ftrace callback
all three of these steps will do a recursion protection.
There's no reason to do one if the previous caller already
did. The recursion that we are protecting against will
go through the same steps again.

To prevent the multiple recursion checks, if a recursion
bit is set that is higher than the MAX bit of the current
check, then we know that the check was made by the previous
caller, and we can skip the current check.

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

1 files changed, 9 insertions, 31 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 639b6ab1f04..ce8c3d68292 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -158,25 +158,15 @@ ftrace_global_list_func(unsigned long ip, unsigned long parent_ip,
 {
 	int bit;
 
-	if (in_interrupt()) {
-		if (in_nmi())
-			bit = TRACE_GLOBAL_NMI_BIT;
-
-		else if (in_irq())
-			bit = TRACE_GLOBAL_IRQ_BIT;
-		else
-			bit = TRACE_GLOBAL_SIRQ_BIT;
-	} else
-		bit = TRACE_GLOBAL_BIT;
-
-	if (unlikely(trace_recursion_test(bit)))
+	bit = trace_test_and_set_recursion(TRACE_GLOBAL_START, TRACE_GLOBAL_MAX);
+	if (bit < 0)
 		return;
 
-	trace_recursion_set(bit);
 	do_for_each_ftrace_op(op, ftrace_global_list) {
 		op->func(ip, parent_ip, op, regs);
 	} while_for_each_ftrace_op(op);
-	trace_recursion_clear(bit);
+
+	trace_clear_recursion(bit);
 }
 
 static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
@@ -4145,26 +4135,14 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
 		       struct ftrace_ops *ignored, struct pt_regs *regs)
 {
 	struct ftrace_ops *op;
-	unsigned int bit;
+	int bit;
 
 	if (function_trace_stop)
 		return;
 
-	if (in_interrupt()) {
-		if (in_nmi())
-			bit = TRACE_INTERNAL_NMI_BIT;
-
-		else if (in_irq())
-			bit = TRACE_INTERNAL_IRQ_BIT;
-		else
-			bit = TRACE_INTERNAL_SIRQ_BIT;
-	} else
-		bit = TRACE_INTERNAL_BIT;
-
-	if (unlikely(trace_recursion_test(bit)))
-			return;
-
-	trace_recursion_set(bit);
+	bit = trace_test_and_set_recursion(TRACE_LIST_START, TRACE_LIST_MAX);
+	if (bit < 0)
+		return;
 
 	/*
 	 * Some of the ops may be dynamically allocated,
@@ -4176,7 +4154,7 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
 			op->func(ip, parent_ip, op, regs);
 	} while_for_each_ftrace_op(op);
 	preempt_enable_notrace();
-	trace_recursion_clear(bit);
+	trace_clear_recursion(bit);
 }
 
 /*