linux-kernel - RE: bnx2x_sriov.c: Missing switch/case breaks?

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Message-ID: <979A8436335E3744ADCD3A9F2A2B68A52AF1A7FF@SJEXCHMB10.corp.ad.broadcom.com>
Date:	Sat, 14 Dec 2013 13:26:19 +0000
From:	Yuval Mintz <yuvalmin@...adcom.com>
To:	Joe Perches <joe@...ches.com>
CC:	Ariel Elior <ariele@...adcom.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: RE: bnx2x_sriov.c: Missing switch/case breaks?

> > > Hi Ariel.
> > >
> > > I wrote a little checkpatch script to look for missing
> > > switch/case breaks.
> > >
> > > http://www.kernelhub.org/?msg=379933&p=2
> > >
> > > There are _many_ instances of case blocks in sriov.c
> > > that could be missing breaks as they use fall-throughs.
> > >
> > > It would be good if these are actually intended to be
> > > fall-throughs to add a /* fall-through */ comment between
> > > each case block.
> > >
> > Hi Joe,
> 
> Hi Yuval.
> 
> > The `vfop' part of the code contains a lot of usage of the
> `bnx2x_vfop_finalize()',
> > which either goto or return at the end of almost every case.
> > "Normal" analysis tools/scripts fail to recognize them as  valid case
> breaks.
> >
> > Adding `fallthrough' comments would make little sense, as this is not the
> real
> > behavior; Perhaps we need some alternative comment? (something in the
> line
> > of `macro case break')
> 
> No idea.  It's certainly an ugly macro.
> 

True.

> This does have a fallthrough path though when
> (rc == 0  && next == VFOP_VERIFY_PEND) so

This is a very rare path - there's exactly one place in the bnx2x code
Where `next == VFOP_VERIFY_PEND' (also notice this path prints an
error, so this is obviously not the expected behaviour).

> maybe there should be a break after most all
> uses of this macro anyway.  When next is

Won't some static code analysis tools regard such `break' calls as
unreachable code?

> VFOP_VERIFY_PEND, then a "fall-through" comment
> would be appropriate.
> 
> cheers, Joe

Thanks,
Yuval
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