linux-kernel - [for-linus][PATCH 10/11] tracing/hwlat: Dont ignore outer-loop duration when calculating max

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Date:   Sun, 13 Oct 2019 13:43:52 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org,
        "Srivatsa S. Bhat (VMware)" <srivatsa@...il.mit.edu>
Subject: [for-linus][PATCH 10/11] tracing/hwlat: Dont ignore outer-loop duration when calculating
 max_latency

From: "Srivatsa S. Bhat (VMware)" <srivatsa@...il.mit.edu>

max_latency is intended to record the maximum ever observed hardware
latency, which may occur in either part of the loop (inner/outer). So
we need to also consider the outer-loop sample when updating
max_latency.

Link: http://lkml.kernel.org/r/157073345463.17189.18124025522664682811.stgit@srivatsa-ubuntu

Fixes: e7c15cd8a113 ("tracing: Added hardware latency tracer")
Cc: stable@...r.kernel.org
Signed-off-by: Srivatsa S. Bhat (VMware) <srivatsa@...il.mit.edu>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_hwlat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index a0251a78807d..862f4b0139fc 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -256,6 +256,8 @@ static int get_sample(void)
 		/* Keep a running maximum ever recorded hardware latency */
 		if (sample > tr->max_latency)
 			tr->max_latency = sample;
+		if (outer_sample > tr->max_latency)
+			tr->max_latency = outer_sample;
 	}
 
 out:
-- 
2.23.0