linux-kernel - Re: Is kernel-FD-auto-close exactly equal to explicit-FD-close?

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Date:	Tue, 16 Aug 2016 20:14:05 +0530
From:	Ajay Garg <ajaygargnsit@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Is kernel-FD-auto-close exactly equal to explicit-FD-close?

Just discovered that calling "exit(1)" calls "fcloseall()".
But as I notice, the opened-serial-port (via "open()" call) is also
closed at binary exit.

So, is the serial-port closed by hidden "fcloseall()" call, or by the kernel?
Moreover, is this equivalent to calling explicit "close()" call on the
serial-port-FD?

Thanks and Regards,
Ajay

On Tue, Aug 16, 2016 at 5:29 PM, Ajay Garg <ajaygargnsit@...il.com> wrote:
> Hi All.
>
> We have deployed a simple C-application on an embedded-platform
> running Linux, and we spuriously observe file-corruption. In
> particular, there is an all-important "config" file, and some of its
> lines are lost spuriously.
>
> Now, our application opens quite a few files on the file-systems, and
> one serial-port.
> During the course, if an error occurs, we simply "exit(1)" the binary,
> without any special code for closing any opened-file-descriptors.
>
> I tested with "lsof", and confirmed that after binary exit, any
> open-file-descriptors are closed (automatically by kernel).
>
>
> With this as the background, I revisit my question :: Is
> kernel-file-descriptor-auto-close exactly equal to
> explicit-file-descriptor-close?
>
> Will be grateful for pointers; as of now, nightmares have begun striking me.
>
>
> Thanks and Regards,
> Ajay

-- 
Regards,
Ajay