Linux Virtualization - Jan 2016 - [PATCH v2 0/3] checkpatch: handling of memory barriers

As part of memory barrier cleanup, this patchset
extends checkpatch to make it easier to stop
incorrect memory barrier usage.

This applies on top of my series
	arch: barrier cleanup + barriers for virt
and will be included in the next version of the series.

Changes from v2:
	catch optional\s* before () in barriers
	rewrite using qr{} instead of map

Michael S. Tsirkin (3):
  checkpatch.pl: add missing memory barriers
  checkpatch: check for __smp outside barrier.h
  checkpatch: add virt barriers

 scripts/checkpatch.pl | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

-- 
MST

SMP-only barriers were missing in checkpatch.pl

Refactor code slightly to make adding more variants easier.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 scripts/checkpatch.pl | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 2b3c228..97b8b62 100755
--- 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;
+		my $all_barriers = qr{
+			$barriers|
+			smp_($smp_barriers)
+		}x;
+
+		if ($line =~ /\b($all_barriers)\s*\(/) {
 			if (!ctx_has_comment($first_line, $linenr)) {
 				WARN("MEMORY_BARRIER",
 				     "memory barrier without comment\n" . $herecurr);
-- 
MST

Introduction of __smp barriers cleans up a bunch of duplicate code, but
it gives people an additional handle onto a "new" set of barriers -
just
because they're prefixed with __* unfortunately doesn't stop anyone from
using it (as happened with other arch stuff before.)

Add a checkpatch test so it will trigger a warning.

Reported-by: Russell King <linux at arm.linux.org.uk>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 scripts/checkpatch.pl | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 97b8b62..a96adcb 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5141,6 +5141,16 @@ sub process {
 			}
 		}
 
+		my $underscore_smp_barriers = qr{__smp_($smp_barriers)}x;
+
+		if ($realfile !~ m@^include/asm-generic/@ &&
+		    $realfile !~ m@/barrier\.h$@ &&
+		    $line =~ m/\b($underscore_smp_barriers)\s*\(/ &&
+		    $line !~ m/^.\s*\#\s*define\s+($underscore_smp_barriers)\s*\(/) {
+			WARN("MEMORY_BARRIER",
+			     "__smp memory barriers shouldn't be used outside barrier.h and
asm-generic\n" . $herecurr);
+		}
+
 # check for waitqueue_active without a comment.
 		if ($line =~ /\bwaitqueue_active\s*\(/) {
 			if (!ctx_has_comment($first_line, $linenr)) {
-- 
MST

Add virt_ barriers to list of barriers to check for
presence of a comment.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 scripts/checkpatch.pl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index a96adcb..5ca272b 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5131,7 +5131,8 @@ sub process {
 		}x;
 		my $all_barriers = qr{
 			$barriers|
-			smp_($smp_barriers)
+			smp_($smp_barriers)|
+			virt_($smp_barriers)
 		}x;
 
 		if ($line =~ /\b($all_barriers)\s*\(/) {
-- 
MST

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);

On Sun, 2016-01-10 at 13:57 +0200, Michael S. Tsirkin
wrote:
> Introduction of __smp barriers cleans up a bunch of duplicate code, but
> it gives people an additional handle onto a "new" set of barriers
- just
> because they're prefixed with __* unfortunately doesn't stop anyone
from
> using it (as happened with other arch stuff before.)
> 
> Add a checkpatch test so it will trigger a warning.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -5141,6 +5141,16 @@ sub process {
> ?			}
> ?		}
> ?
> +		my $underscore_smp_barriers = qr{__smp_($smp_barriers)}x;
another unnecessary capture group
> +
> +		if ($realfile !~ m@^include/asm-generic/@ &&
> +		????$realfile !~ m@/barrier\.h$@ &&
> +		????$line =~ m/\b($underscore_smp_barriers)\s*\(/ &&
> +		????$line !~ m/^.\s*\#\s*define\s+($underscore_smp_barriers)\s*\(/) {
> +			WARN("MEMORY_BARRIER",
> +			?????"__smp memory barriers shouldn't be used outside
barrier.h and asm-generic\n" . $herecurr);
> +		}
> +
> ?# check for waitqueue_active without a comment.
> ?		if ($line =~ /\bwaitqueue_active\s*\(/) {
> ?			if (!ctx_has_comment($first_line, $linenr)) {