linux-kernel - Re: [PATCH 1/3] checkpatch.pl: add missing memory barriers

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Date:	Mon, 4 Jan 2016 22:45:19 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Joe Perches <joe@...ches.com>
Cc:	linux-kernel@...r.kernel.org,
	"Cc : Andy Whitcroft" <apw@...onical.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	virtualization@...ts.linux-foundation.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	David Miller <davem@...emloft.net>, linux-ia64@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-metag@...r.kernel.org, linux-mips@...ux-mips.org,
	x86@...nel.org, user-mode-linux-devel@...ts.sourceforge.net,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	xen-devel@...ts.xenproject.org, Ingo Molnar <mingo@...nel.org>,
	Tony Lindgren <tony@...mide.com>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [PATCH 1/3] checkpatch.pl: add missing memory barriers

On Mon, Jan 04, 2016 at 08:07:40AM -0800, Joe Perches wrote:
> On Mon, 2016-01-04 at 13:36 +0200, Michael S. Tsirkin wrote:
> > SMP-only barriers were missing in checkpatch.pl
> > 
> > Refactor code slightly to make adding more variants easier.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> >  scripts/checkpatch.pl | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index 2b3c228..0245bbe 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -5116,7 +5116,14 @@ sub process {
> >  			}
> >  		}
> >  # check for memory barriers without a comment.
> > -		if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) {
> > +
> > +		my @barriers = ('mb', 'rmb', 'wmb', 'read_barrier_depends');
> > +		my @smp_barriers = ('smp_store_release', 'smp_load_acquire', 'smp_store_mb');
> > +
> > +		@smp_barriers = (@smp_barriers, map {"smp_" . $_} @barriers);
> 
> I think using map, which so far checkpatch doesn't use,
> makes smp_barriers harder to understand and it'd be
> better to enumerate them.

Okay - I'll rewrite using foreach.

> > +		my $all_barriers = join('|', (@barriers, @smp_barriers));
> > +
> > +		if ($line =~ /\b($all_barriers)\(/) {
> 
> It would be better to use /\b$all_barriers\s*\(/
> as there's no reason for the capture and there
> could be a space between the function and the
> open parenthesis.

That's the way it was - space before ( will trigger other
warnings. But sure, ok.

> 
> >  			if (!ctx_has_comment($first_line, $linenr)) {
> >  				WARN("MEMORY_BARRIER",
> >  				     "memory barrier without comment\n" . $herecurr);
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