linux-kernel - Re: [PATCH v2] jiffies: Cast to unsigned long for secs_to

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Message-ID: <04c2959e-bf41-4483-b30f-8b4b6a81242b@kernel.org>
Date: Fri, 31 Jan 2025 09:52:39 +0100
From: Jiri Slaby <jirislaby@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>,
 Easwar Hariharan <eahariha@...ux.microsoft.com>,
 Anna-Maria Behnsen <anna-maria@...utronix.de>,
 Geert Uytterhoeven <geert@...ux-m68k.org>,
 Luiz Augusto von Dentz <luiz.von.dentz@...el.com>,
 Miguel Ojeda <ojeda@...nel.org>, open list <linux-kernel@...r.kernel.org>
Cc: stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
 kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] jiffies: Cast to unsigned long for secs_to_jiffies()
 conversion

On 31. 01. 25, 9:30, Thomas Gleixner wrote:
> On Fri, Jan 31 2025 at 08:06, Jiri Slaby wrote:
>> On 30. 01. 25, 20:26, Easwar Hariharan wrote:
>>> While converting users of msecs_to_jiffies(), lkp reported that some
>>> range checks would always be true because of the mismatch between the
>>> implied int value of secs_to_jiffies() vs the unsigned long
>>> return value of the msecs_to_jiffies() calls it was replacing. Fix this
>>> by casting secs_to_jiffies() values as unsigned long.
>>>
>>> Fixes: b35108a51cf7ba ("jiffies: Define secs_to_jiffies()")
>>> CC: stable@...r.kernel.org # 6.13+
>>> CC: Andrew Morton <akpm@...ux-foundation.org>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Closes: https://lore.kernel.org/oe-kbuild-all/202501301334.NB6NszQR-lkp@intel.com/
>>> Signed-off-by: Easwar Hariharan <eahariha@...ux.microsoft.com>
>>> ---
>>>    include/linux/jiffies.h | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
>>> index ed945f42e064..0ea8c9887429 100644
>>> --- a/include/linux/jiffies.h
>>> +++ b/include/linux/jiffies.h
>>> @@ -537,7 +537,7 @@ static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
>>>     *
>>>     * Return: jiffies value
>>>     */
>>> -#define secs_to_jiffies(_secs) ((_secs) * HZ)
>>> +#define secs_to_jiffies(_secs) (unsigned long)((_secs) * HZ)
>>
>> Could you just switch the fun to an inline instead?
> 
> It's a macro so it can be used in static initializers.

It's the only one from the *_to_jiffies() family we offer. And I fail to 
find such a use (by a quick grep, it only might be hidden)? People 
apparently use "* HZ" in initializers...

So sure, iff there is this intention for this very one, keep it as macro.

-- 
js
suse labs