Re: [PATCH v2 09/15] timers: Add a warning to usleep_range_state() for wrong order of arguments

[Anna-Maria Behnsen <anna-maria@linutronix.de>]

Frederic Weisbecker <frederic@kernel.org> writes:

> 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@canonical.com>
>> Cc: Joe Perches <joe@perches.com>
>> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.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

yes!

>>  	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?

I'll keep it but drop the link to the
Documentation/timers/timers-howto.rst which will be removed.

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