linux-kernel - Re: [PATCH] tools/gpio: prevent resource leak

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Message-ID: <CACRpkdZfTbrPLFGH5akY=od8Rma=2c6F=nPz2nmAz2my_f7OeQ@mail.gmail.com>
Date:   Thu, 9 Nov 2023 13:50:02 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Kent Gibson <warthog618@...il.com>
Cc:     heminhong <heminhong@...inos.cn>, brgl@...ev.pl, andy@...nel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools/gpio: prevent resource leak

On Thu, Nov 9, 2023 at 1:36 PM Kent Gibson <warthog618@...il.com> wrote:
> On Thu, Nov 09, 2023 at 04:54:19PM +0800, heminhong wrote:

> > In the main() function, the open() function is used to open the file.
> > When the file is successfully opened, fd is used to interact with the file,
> > but the fd is not closed, it will cause resource leak.
>
> All open files are automatically closed when a process exits.
> That includes both those returned by open() and by the GPIO ioctls.
> So explicitly closing them here before exiting is redundant.

Yup. And this is one of the reasons why we have the character device
in the first place.

The character device gets released and all GPIOs are released
if the program crashes.

You can imagine what happens with the sysfs ABI if a bash
script crashes halfway through some complex allocating and
banging GPIOs left and right. Not good at all.

Yours,
Linus Walleij