trace/osnoise: Make 'noise' variable s64 in run_osnoise()

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.

Link: https://lkml.kernel.org/r/acd7cd6e7d56b798a298c3bc8139a390b3c4ab52.1624986368.git.bristot@redhat.com
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>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 085a83d..cc1faca 100644 (file)
--- 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;
 
        /*