linux-kernel - Re: [PATCH v2 1/3] checkpatch.pl: add missing memory barriers

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Date:	Sun, 10 Jan 2016 07:07:05 -0800
From:	Joe Perches <joe@...ches.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, 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 v2 1/3] checkpatch.pl: add missing memory barriers

On Sun, 2016-01-10 at 13:56 +0200, Michael S. Tsirkin wrote:
> SMP-only barriers were missing in checkpatch.pl
> 
> Refactor code slightly to make adding more variants easier.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -5116,7 +5116,25 @@ 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 = qr{
> +			mb|
> +			rmb|
> +			wmb|
> +			read_barrier_depends
> +		}x;
> +		my $smp_barriers = qr{
> +			store_release|
> +			load_acquire|
> +			store_mb|
> +			($barriers)
> +		}x;

If I use a variable called $smp_barriers, I'd expect
it to actually be the smp_barriers, not to have to
prefix it with smp_ before using it.

		my $smp_barriers = qr{
			smp_store_release|
			smp_load_acquire|
			smp_store_mb|
			smp_read_barrier_depends
		}x;

or

		my $smp_barriers = qr{
			smp_(?:store_release|load_acquire|store_mb|read_barrier_depends)
		}x;

 
> +		my $all_barriers = qr{
> +			$barriers|
> +			smp_($smp_barriers)
> +		}x;

And this shouldn't have a capture group.

		my $all_barriers = qr{
			$barriers|
			$smp_barriers
		}x;		
> +
> +		if ($line =~ /\b($all_barriers)\s*\(/) {

This doesn't need the capture group either (?:all_barriers)

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