tracing: Record and show NMI state

The latency tracer format has a nice column to indicate IRQ state, but
this is not able to tell us about NMI state.

When tracing perf interrupt handlers (which often run in NMI context)
it is very useful to see how the events nest.

Link: http://lkml.kernel.org/r/20160318153022.105068893@infradead.org

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 282982195e09..0bb9cf2d53e6 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -389,7 +389,9 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
         char irqs_off;
         int hardirq;
         int softirq;
+        int nmi;
 
+        nmi = entry->flags & TRACE_FLAG_NMI;
         hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
         softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
 
@@ -415,10 +417,12 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
         }
 
         hardsoft_irq =
+                (nmi && hardirq)     ? 'Z' :
+                nmi                  ? 'z' :
                 (hardirq && softirq) ? 'H' :
-                hardirq ? 'h' :
-                softirq ? 's' :
-                '.';
+                hardirq              ? 'h' :
+                softirq              ? 's' :
+                                       '.' ;
 
         trace_seq_printf(s, "%c%c%c",
                          irqs_off, need_resched, hardsoft_irq);