tracing/hwlat: Report total time spent in all NMIs during the sample

commit 98dc19c11470ee6048aba723d77079ad2cda8a52 upstream.

nmi_total_ts is supposed to record the total time spent in *all* NMIs
that occur on the given CPU during the (active portion of the)
sampling window. However, the code seems to be overwriting this
variable for each NMI, thereby only recording the time spent in the
most recent NMI. Fix it by accumulating the duration instead.

Link: http://lkml.kernel.org/r/157073343544.17189.13911783866738671133.stgit@srivatsa-ubuntu
Fixes: 7b2c86250122 ("tracing: Add NMI tracing in hwlat detector")
Cc: stable@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 1e6db9cbe4dc518b0f0a482cf1c7e5eeffa0a3c4..1e9a404cee2bdbe0f5235d907484d365b54f3522 100644 (file)
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -150,7 +150,7 @@ void trace_hwlat_callback(bool enter)
                if (enter)
                        nmi_ts_start = time_get();
                else
-                       nmi_total_ts = time_get() - nmi_ts_start;
+                       nmi_total_ts += time_get() - nmi_ts_start;
        }
 
        if (enter)