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

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Message-ID: <Z2KJ8C7nOOK2tJ1X@pathway.suse.cz>
Date: Wed, 18 Dec 2024 09:38:36 +0100
From: Petr Mladek <pmladek@...e.com>
To: Easwar Hariharan <eahariha@...ux.microsoft.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	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 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?

It might work in theory but I do not feel comfortable with it.
Also I would expect a compiler warning.

If you really want to use schedule_work() then please
also define the structure with DECLARE_WORK()
and use cancel_work_sync() in livepatch_callbacks_mod_exit().

Best Regards,
Petr