[PATCH v4 15/27] tracing: Employ trace_rcu_{enter,exit}()

[Peter Zijlstra]

Replace the opencoded (and incomplete) RCU manipulations with the new
helpers to ensure a regular RCU context when calling into
__ftrace_trace_stack().

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c |   19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2989,24 +2989,11 @@ void __trace_stack(struct trace_array *t
 		   int pc)
 {
 	struct trace_buffer *buffer = tr->array_buffer.buffer;
+	int rcu_flags;
 
-	if (rcu_is_watching()) {
-		__ftrace_trace_stack(buffer, flags, skip, pc, NULL);
-		return;
-	}
-
-	/*
-	 * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
-	 * but if the above rcu_is_watching() failed, then the NMI
-	 * triggered someplace critical, and rcu_irq_enter() should
-	 * not be called from NMI.
-	 */
-	if (unlikely(in_nmi()))
-		return;
-
-	rcu_irq_enter_irqsave();
+	rcu_flags = trace_rcu_enter();
 	__ftrace_trace_stack(buffer, flags, skip, pc, NULL);
-	rcu_irq_exit_irqsave();
+	trace_rcu_exit(rcu_flags);
 }
 
 /**