Date:   Thu, 11 Nov 2021 10:11:21 +0100
From:   Marco Elver <elver@google.com>
To:     Valentin Schneider <valentin.schneider@arm.com>
Cc:     linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        linuxppc-dev@lists.ozlabs.org, linux-kbuild@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Mike Galbraith <efault@gmx.de>,
        Dmitry Vyukov <dvyukov@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH v2 4/5] kscan: Use preemption model accessors
Message-ID: <YYzeOQNFmuieCk3T@elver.google.com>
References: <20211110202448.4054153-1-valentin.schneider@arm.com>
 <20211110202448.4054153-5-valentin.schneider@arm.com>
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Subject s/kscan/kcsan/

On Wed, Nov 10, 2021 at 08:24PM +0000, Valentin Schneider wrote:
> Per PREEMPT_DYNAMIC, checking CONFIG_PREEMPT doesn't tell you the actual
> preemption model of the live kernel. Use the newly-introduced accessors
> instead.
> 
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>

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

Though it currently doesn't compile as a module due to missing
EXPORT_SYMBOL of is_preempt*().

> ---
>  kernel/kcsan/kcsan_test.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
> index dc55fd5a36fc..14d811eb9a21 100644
> --- a/kernel/kcsan/kcsan_test.c
> +++ b/kernel/kcsan/kcsan_test.c
> @@ -1005,13 +1005,13 @@ static const void *nthreads_gen_params(const void *prev, char *desc)
>  	else
>  		nthreads *= 2;
>  
> -	if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
> +	if (!is_preempt_full() || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
>  		/*
>  		 * Without any preemption, keep 2 CPUs free for other tasks, one
>  		 * of which is the main test case function checking for
>  		 * completion or failure.
>  		 */
> -		const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
> +		const long min_unused_cpus = is_preempt_none() ? 2 : 0;
>  		const long min_required_cpus = 2 + min_unused_cpus;
>  
>  		if (num_online_cpus() < min_required_cpus) {
> -- 
> 2.25.1