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Subject[PATCH 1/2] trace/osnoise: Make 'noise' variable s64 in run_osnoise()
Date
Dab Carpenter reported that:

The patch bce29ac9ce0b: "trace: Add osnoise tracer" from Jun 22,
2021, leads to the following static checker warning:

kernel/trace/trace_osnoise.c:1103 run_osnoise()
warn: unsigned 'noise' is never less than zero.

In this part of the code:

1100 /*
1101 * This shouldn't happen.
1102 */
1103 if (noise < 0) {
^^^^^^^^^
1104 osnoise_taint("negative noise!");
1105 goto out;
1106 }
1107

And the static checker is right because 'noise' is u64.

Make noise s64 and keep the check. It is important to check if
the time read is behaving correctly - so we can trust the results.

I also re-arranged some variable declarations.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: linux-kernel@vger.kernel.org
Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
---
kernel/trace/trace_osnoise.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 085a83de98ad..cc1faca1a620 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1042,15 +1042,16 @@ 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;
struct trace_array *tr = osnoise_trace;
u64 start, sample, last_sample;
u64 last_int_count, int_count;
+ s64 noise = 0, max_noise = 0;
s64 total, last_total = 0;
struct osnoise_sample s;
unsigned int threshold;
- int hw_count = 0;
u64 runtime, stop_in;
+ u64 sum_noise = 0;
+ int hw_count = 0;
int ret = -1;

/*
--
2.31.1
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