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SubjectRe: [PATCH][next] trace: osnoise: Fix u64 less than zero comparison
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On 6/29/21 6:52 PM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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.

Ops! concurrent bug fixing.

Dan Carpenter reported the same bug (and another problem), and I was working in
the patches... I saw yours after sending his ones:

https://lore.kernel.org/lkml/acd7cd6e7d56b798a298c3bc8139a390b3c4ab52.1624986368.git.bristot@redhat.com/

The patches do the same fix, but there it also:

- Made also max_noise s64 (it is snapshot of noise).
- Arranged the declarations in the inverted christmas tree.

> Addresses-Coverity: ("Unsigned compared against 0")
> Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Steven, can we merge the flags?

-- Daniel

> ---
> 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;
>

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