linux-kernel - Re: [PATCH v4 2/2] livepatch: Convert timeouts to secs_to

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Message-ID: <195abda2-8209-45aa-9652-f981a5de2eae@linux.microsoft.com>
Date: Wed, 18 Dec 2024 09:35:46 -0800
From: Easwar Hariharan <eahariha@...ux.microsoft.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
 Petr Mladek <pmladek@...e.com>, Andrew Morton <akpm@...ux-foundation.org>
Cc: eahariha@...ux.microsoft.com, Alexander Gordeev <agordeev@...ux.ibm.com>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Jiri Kosina <jikos@...nel.org>, Miroslav Benes <mbenes@...e.cz>,
 Joe Lawrence <joe.lawrence@...hat.com>, linux-s390@...r.kernel.org,
 linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Subject: Re: [PATCH v4 2/2] livepatch: Convert timeouts to secs_to_jiffies()

On 12/18/2024 12:48 AM, Christophe Leroy wrote:
> 
> 
> Le 18/12/2024 à 09:38, Petr Mladek a écrit :
>> On Tue 2024-12-17 23:09:59, Easwar Hariharan wrote:
>>> Commit b35108a51cf7 ("jiffies: Define secs_to_jiffies()") introduced
>>> secs_to_jiffies(). As the value here is a multiple of 1000, use
>>> secs_to_jiffies() instead of msecs_to_jiffies to avoid the
>>> multiplication.
>>>
>>> This is converted using scripts/coccinelle/misc/secs_to_jiffies.cocci
>>> with
>>> the following Coccinelle rules:
>>>
>>> @@ constant C; @@
>>>
>>> - msecs_to_jiffies(C * 1000)
>>> + secs_to_jiffies(C)
>>>
>>> @@ constant C; @@
>>>
>>> - msecs_to_jiffies(C * MSEC_PER_SEC)
>>> + secs_to_jiffies(C)
>>>
>>> While here, replace the schedule_delayed_work() call with a 0 timeout
>>> with an immediate schedule_work() call.
>>>
>>> --- a/samples/livepatch/livepatch-callbacks-busymod.c
>>> +++ b/samples/livepatch/livepatch-callbacks-busymod.c
>>> @@ -44,8 +44,7 @@ static void busymod_work_func(struct work_struct
>>> *work)
>>>   static int livepatch_callbacks_mod_init(void)
>>>   {
>>>       pr_info("%s\n", __func__);
>>> -    schedule_delayed_work(&work,
>>> -        msecs_to_jiffies(1000 * 0));
>>> +    schedule_work(&work);
>>
>> Is it safe to use schedule_work() for struct delayed_work?
> 
> Should be, but you are right it should then be a standard work not a
> delayed work.
> 
> So probably the easiest is to keep
> 
>     schedule_delayed_work(&work, 0)
> 
> And eventually changing it to a not delayed work could be a follow-up
> patch.
> 
>>

Thanks for the catch, Petr! This suggestion would effectively revert
this patch to the v3 version, albeit with some extra explanation in the
commit message. I'd propose just keeping the v3 in the next branch where
it is.

Andrew, Petr, Christophe, what do you think?