linux-kernel - Re: [PATCH 3/3] staging:iio:ad2s1210: Add write_raw to handle frequency

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Message-ID: <20180313143324.vlusixa522rqaeoy@smtp.gmail.com>
Date:   Tue, 13 Mar 2018 11:33:24 -0300
From:   Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     devel@...verdev.osuosl.org, Graff Yang <graff.yang@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        linux-iio@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Hartmut Knaack <knaack.h@....de>, daniel.baluta@....com,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH 3/3] staging:iio:ad2s1210: Add write_raw to handle
 frequency

On 03/13, Dan Carpenter wrote:
> On Tue, Mar 13, 2018 at 10:06:29AM -0300, Rodrigo Siqueira wrote:
> > On 03/13, Dan Carpenter wrote:
> >
> > > Ah...  I see why you did the ERROR_MESSAGE define, to get around the 80
> > > character limit.  Don't do that.  Just go over 80 characters if you need
> > > to.
> > > 
> > > 
> > > > +					"fclkin");
> > > > +				ret = -EINVAL;
> > > > +				goto error_ret;
> > > 
> > > Direct returns are better.  Less chance of bugs statistically.
> > 
> > I totally get your point here, and I will fix it. However, just for
> > curiosity, why goto in this situation has more chance to generate bugs
> > statically?
> > 
> 
> This is a do-nothing goto.  I normally consider do-nothing gotos and
> do-everything gotos basically cousins but in this case it's probably
> unfair since it already has other labels.
> 
> Do-everything gotos are the most error prone way of doing error
> handling.  I've reviewed a lot of static checker warnings and it really
> is true.  I can't give you like a percent figure but do-everything error
> handling is a lot buggier than normal kernel style.
> 
> This style of error handling is supposed to prevent returning without
> unlocking bugs.  I once looked through the git log and counted missing
> unlock bugs and my conclusion was that it basically doesn't work for
> preventing bugs.  The kind of people who just add random returns will do
> it regardless of the error handling style.  There was even one driver
> that indented locked code like this:
> 
> 	lock(); {
> 		blah blah blah;
> 	} unlock();
> 
> When the driver was first submitted, it already had a missing unlock
> bug.  I don't think style helps slow people down who are in a hurry.
> 
> The other thing about do-nothing gotos is that you introduce the
> possibility of "forgot to set the error code" bugs which wasn't there
> before.
> 
> regards,
> dan carpenter
> 
> 
> 
> 
> 
> 
> 
> 
> So actually "error_ret" seems like a pretty reasonable name for a
> do-nothing goto.  I no
> 
> I've looked at a lot of error handling and this kind of error handling
> is more error prone.  The single exit path thing is supposed to prevent
> bugs like not dropping the lock on exit and I've looked through the logs
> and counted bugs to see if it works and I don't think it does.  The
> people who forget to unlock will forget to unlock regardless of the
> error handling style.
> 

Thanks for the great explanation :)
 
> 
> 
> 
> > I will send a v2 with your recommendantions.
> > Thanks for the review and feedbacks :)
> >  
> > > regards,
> > > dan carpenter
> > > 
> > _______________________________________________
> > devel mailing list
> > devel@...uxdriverproject.org
> > http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

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