linux-kernel - Re: [PATCH v2 09/15] timers: Add a warning to usleep_range

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Message-ID: <ZwZ1ePAzuyJBlxNy@localhost.localdomain>
Date: Wed, 9 Oct 2024 14:22:16 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: Thomas Gleixner <tglx@...utronix.de>, Jonathan Corbet <corbet@....net>,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Andy Whitcroft <apw@...onical.com>, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2 09/15] timers: Add a warning to usleep_range_state()
 for wrong order of arguments

Le Wed, Sep 11, 2024 at 07:13:35AM +0200, Anna-Maria Behnsen a écrit :
> There is a warning in checkpatch script that triggers, when min and max
> arguments of usleep_range_state() are in reverse order. This check does
> only cover callsites which uses constants. Move this check into the code as
> a WARN_ON_ONCE() to also cover callsites not using constants and get rid of
> it in checkpatch.
> 
> Cc: Andy Whitcroft <apw@...onical.com>
> Cc: Joe Perches <joe@...ches.com>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
> ---
>  kernel/time/sleep_timeout.c | 2 ++
>  scripts/checkpatch.pl       | 4 ----
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/time/sleep_timeout.c b/kernel/time/sleep_timeout.c
> index 21f412350b15..4b805d7e1903 100644
> --- a/kernel/time/sleep_timeout.c
> +++ b/kernel/time/sleep_timeout.c
> @@ -364,6 +364,8 @@ void __sched usleep_range_state(unsigned long min, unsigned long max, unsigned i
>  	ktime_t exp = ktime_add_us(ktime_get(), min);
>  	u64 delta = (u64)(max - min) * NSEC_PER_USEC;
>  
> +	WARN_ON_ONCE(max < min);
> +

Should it try to "fix" to avoid overflow?

if WARN_ON_ONCE(max < min)
    delta = 0

>  	for (;;) {
>  		__set_current_state(state);
>  		/* Do not return before the requested sleep time has elapsed */
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 39032224d504..ba3359bdd1fa 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -7088,10 +7088,6 @@ sub process {
>  			if ($min eq $max) {
>  				WARN("USLEEP_RANGE",
>  				     "usleep_range should not use min == max args; see Documentation/timers/timers-howto.rst\n" . "$here\n$stat\n");
> -			} elsif ($min =~ /^\d+$/ && $max =~ /^\d+$/ &&
> -				 $min > $max) {
> -				WARN("USLEEP_RANGE",
> -				     "usleep_range args reversed, use min then max; see Documentation/timers/timers-howto.rst\n" . "$here\n$stat\n");

Perhaps it doesn't hurt to keep the static check?

Thanks.
>  			}
>  		}
>  
> 
> -- 
> 2.39.2
>