[for-next][PATCH 2/2] tracing: Record and show NMI state

[Steven Rostedt]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c        |  1 +
 kernel/trace/trace.h        |  1 +
 kernel/trace/trace_output.c | 10 +++++++---
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index cb2b708e4ea7..7bdf8ba323ec 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1664,6 +1664,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 #else
 		TRACE_FLAG_IRQS_NOSUPPORT |
 #endif
+		((pc & NMI_MASK    ) ? TRACE_FLAG_NMI     : 0) |
 		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
 		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
 		(tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 39588c23dd8b..3fff4adfd431 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -125,6 +125,7 @@ enum trace_flag_type {
 	TRACE_FLAG_HARDIRQ		= 0x08,
 	TRACE_FLAG_SOFTIRQ		= 0x10,
 	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
+	TRACE_FLAG_NMI			= 0x40,
 };
 
 #define TRACE_BUF_SIZE		1024
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);
-- 
2.7.0