[PATCH v2 7/9] tracing: Employ trace_rcu_{enter,exit}()

Peter Zijlstra
2020-02-12T21:14:19Z

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@infradead.org>
---
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;
+ unsigned long 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);
}

/**