linux-kernel - Re: [PATCH] auxdisplay: charlcd: delete mdelay in long

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Message-ID: <CANiq72mJQhJ9zkBZ1+qDBjChwy_5i3X12h=uhuic1VEBvTwCFA@mail.gmail.com>
Date:   Mon, 12 Feb 2018 14:26:23 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     Jia-Ju Bai <baijiaju1990@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] auxdisplay: charlcd: delete mdelay in long_sleep

On Mon, Jan 29, 2018 at 7:50 AM, Willy Tarreau <w@....eu> wrote:
> Hi,
>
> On Fri, Jan 26, 2018 at 11:19:15PM +0800, Jia-Ju Bai wrote:
>> The function long_sleep() calls mdelay() when in an interrupt handler.
>> But only charlcd_clear_display() and charlcd_init_display calls
>> long_sleep(), and my tool finds that the two functions
>> are never called in an interrupt handler.
>> Thus mdelay() and in_interrupt() are not necessary.
>>
>> This is found by a static analysis tool named DCNS written by myself.
>
> Looks good. This code is extremely old (started in 2.2) so I'm not
> surprised at all that after many changes such parts are not used
> anymore.

By the way, maybe msleep_interruptible() should be used instead?
(since I guess you want a minimum time here, no?). It would also take
care of the jiffies to ms conversion, so the whole long_jump could be
removed.

>
> Acked-by: Willy Tarreau <w@....eu>
>
> Willy