linux-kernel - Re: [PATCH] perf tests switch-tracking: Fix timestamp comparison

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAP-5=fVsgahBhOEOac52PmL0V+n1jqAxzf7n9PVWgWsxq9TvgQ@mail.gmail.com>
Date: Mon, 31 Mar 2025 13:18:31 -0700
From: Ian Rogers <irogers@...gle.com>
To: Leo Yan <leo.yan@....com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, "Liang, Kan" <kan.liang@...ux.intel.com>, 
	James Clark <james.clark@...aro.org>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tests switch-tracking: Fix timestamp comparison

On Mon, Mar 31, 2025 at 10:28 AM Leo Yan <leo.yan@....com> wrote:
>
> The test might fail on the Arm64 platform with the error:
>
>   perf test -vvv "Track with sched_switch"
>   Missing sched_switch events
>
> The issue is caused by incorrect handling of timestamp comparisons. The
> comparison result, a signed 64-bit value, was being directly cast to an
> int, leading to incorrect sorting for sched events.
>
> Fix this by explicitly returning 0, 1, or -1 based on whether the result
> is zero, positive, or negative.

I'm reminded of a Java check I wrote for this:
https://errorprone.info/bugpattern/BadComparable
In clang -Wshorten-64-to-32 looks to cover this. I'll see if we can
clean those warnings up a bit.

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> Fixes: d44bc5582972 ("perf tests: Add a test for tracking with sched_switch")
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>  tools/perf/tests/switch-tracking.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/tests/switch-tracking.c b/tools/perf/tests/switch-tracking.c
> index 8df3f9d9ffd2..6b3aac283c37 100644
> --- a/tools/perf/tests/switch-tracking.c
> +++ b/tools/perf/tests/switch-tracking.c
> @@ -264,7 +264,7 @@ static int compar(const void *a, const void *b)
>         const struct event_node *nodeb = b;
>         s64 cmp = nodea->event_time - nodeb->event_time;
>
> -       return cmp;
> +       return cmp < 0 ? -1 : (cmp > 0 ? 1 : 0);
>  }
>
>  static int process_events(struct evlist *evlist,
> --
> 2.34.1
>