linux-kernel - [PATCH][next] trace: osnoise: Fix u64 less than zero comparison

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Message-Id: <20210629165245.42157-1-colin.king@canonical.com>
Date:   Tue, 29 Jun 2021 17:52:45 +0100
From:   Colin King <colin.king@...onical.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] trace: osnoise: Fix u64 less than zero comparison

From: Colin Ian King <colin.king@...onical.com>

The less than zero comparison of the u64 variable 'noise' is always
false because the variable is unsigned. Since the time_sub macro
can potentially return an -ve vale, make the variable a s64 to
fix the issue.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 kernel/trace/trace_osnoise.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 38aa5e208ffd..02c984560ceb 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1040,11 +1040,11 @@ static void osnoise_stop_tracing(void)
 static int run_osnoise(void)
 {
 	struct osnoise_variables *osn_var = this_cpu_osn_var();
-	u64 noise = 0, sum_noise = 0, max_noise = 0;
+	u64 sum_noise = 0, max_noise = 0;
 	struct trace_array *tr = osnoise_trace;
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;
-	s64 total, last_total = 0;
+	s64 noise = 0, total, last_total = 0;
 	struct osnoise_sample s;
 	unsigned int threshold;
 	int hw_count = 0;
-- 
2.31.1