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>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index cb2b708e4ea76fee6cd9ca494adeb655adc8daec..7bdf8ba323ec80e614bdbaaeb4b0560a6bcdc67a 100644 (file)
--- 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 39588c23dd8b6a0b0f4f1bbd51a845fcaa811076..3fff4adfd431c5093fd5b8e5f53e41d2237e234b 100644 (file)
--- 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 282982195e09ff40ad23f3ab1dca7e572c0ab8e6..0bb9cf2d53e66cfbe33bc5b8ea0068f967e7da7f 100644 (file)
--- 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);