linux-kernel - Re: [PATCH] kcsan: fix printk format string

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Date:   Wed, 21 Apr 2021 15:59:40 +0200
From:   Marco Elver <elver@...gle.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        David Gow <davidgow@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] kcsan: fix printk format string

On Wed, 21 Apr 2021 at 15:51, Arnd Bergmann <arnd@...nel.org> wrote:
> From: Arnd Bergmann <arnd@...db.de>
>
> Printing a 'long' variable using the '%d' format string is wrong
> and causes a warning from gcc:
>
> kernel/kcsan/kcsan_test.c: In function 'nthreads_gen_params':
> include/linux/kern_levels.h:5:25: error: format '%d' expects argument of type 'int', but argument 3 has type 'long int' [-Werror=format=]
>
> Use the appropriate format modifier.
>
> Fixes: f6a149140321 ("kcsan: Switch to KUNIT_CASE_PARAM for parameterized tests")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Marco Elver <elver@...gle.com>

Thank you!

Normally KCSAN patches go through -rcu, but perhaps in this instance
it should be picked up into -tip/locking/core directly, so it goes out
with "kcsan: Switch to KUNIT_CASE_PARAM for parameterized tests".
Paul, Ingo, do you have a preference?

Thanks,
-- Marco

> ---
>  kernel/kcsan/kcsan_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
> index 9247009295b5..a29e9b1a30c8 100644
> --- a/kernel/kcsan/kcsan_test.c
> +++ b/kernel/kcsan/kcsan_test.c
> @@ -981,7 +981,7 @@ static const void *nthreads_gen_params(const void *prev, char *desc)
>                 const long min_required_cpus = 2 + min_unused_cpus;
>
>                 if (num_online_cpus() < min_required_cpus) {
> -                       pr_err_once("Too few online CPUs (%u < %d) for test\n",
> +                       pr_err_once("Too few online CPUs (%u < %ld) for test\n",
>                                     num_online_cpus(), min_required_cpus);
>                         nthreads = 0;
>                 } else if (nthreads >= num_online_cpus() - min_unused_cpus) {
> --
> 2.29.2