linux-kernel - RE: [PATCH] tools/counter: close fd when exit

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Message-ID: <e1259039a99d4f23958c4380e5c0b11f@AcuMS.aculab.com>
Date: Sun, 8 Sep 2024 20:08:23 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Andy Shevchenko' <andy.shevchenko@...il.com>, zhangjiao2
	<zhangjiao2@...s.chinamobile.com>
CC: "wbg@...nel.org" <wbg@...nel.org>, "linux-iio@...r.kernel.org"
	<linux-iio@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] tools/counter: close fd when exit

From: Andy Shevchenko
> Sent: 04 September 2024 00:20
> 
> Tue, Sep 03, 2024 at 04:01:21PM +0800, zhangjiao2 kirjoitti:
> > From: zhang jiao <zhangjiao2@...s.chinamobile.com>
> >
> > close fd when exit the program
> 
> Please, mind English grammar and punctuation.
> Also this doesn't state what the problem is.

After all, when the program exits the kernel closes all the files.

> >  		if (ret == -1) {
> >  			fprintf(stderr, "Error adding watches[%d]: %s\n", i,
> >  				strerror(errno));
> > +			close(fd);
> 
> Since fd is not used in the messaging it's better to close it before printing
> anything. Ditto for other cases.

Unless close() decides to change errno...

> 
> ...
> 
> >  		if (ret != sizeof(event_data)) {
> >  			fprintf(stderr, "Failed to read event data\n");
> > +			close(fd);
> 
> >  			return -EIO;
> 
> Side note: This will return garbage to the userspace. Should be
> 
> 			return EIO;

If that is the return value from main() it is equally invalid.
Valid return values are 0..255 but 128..255 are likely to be
interpreted as 'killed by a signal'.
So really you only get 0..127.
Mostly used as 0 => success and 1 => failure.

	David

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