kernel-janitors.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Colin King <colin.king@canonical.com>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH][next] trace: osnoise: Fix u64 less than zero comparison
Date: Tue, 29 Jun 2021 19:19:25 +0200	[thread overview]
Message-ID: <c74e711e-71c9-df9c-8406-b9e92ef12da0@redhat.com> (raw)
In-Reply-To: <20210629165245.42157-1-colin.king@canonical.com>

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;
> 


  reply	other threads:[~2021-06-29 17:19 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-29 16:52 Colin King
2021-06-29 17:19 ` Daniel Bristot de Oliveira [this message]
2021-06-29 17:21   ` Colin Ian King
2021-06-29 18:55     ` Dan Carpenter
2021-06-30 13:05   ` Steven Rostedt
2021-06-30 13:32     ` Daniel Bristot de Oliveira

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=c74e711e-71c9-df9c-8406-b9e92ef12da0@redhat.com \
    --to=bristot@redhat.com \
    --cc=colin.king@canonical.com \
    --cc=dan.carpenter@oracle.com \
    --cc=kernel-janitors@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=rostedt@goodmis.org \
    --subject='Re: [PATCH][next] trace: osnoise: Fix u64 less than zero comparison' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).