[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@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 <redacted>
Signed-off-by: Michael S. Tsirkin <mst@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@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.

[]

[]

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.

[]

[]

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)) {

On Sun, 2016-01-10 at 07:07 -0800, Joe Perches wrote:

On Sun, 2016-01-10 at 13:56 +0200, Michael S. Tsirkin wrote:

quoted

SMP-only barriers were missing in checkpatch.pl

Refactor code slightly to make adding more variants easier.

[]

quoted

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl

[]

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

That's missing (?:barriers) too.

btw: shouldn't this also have
	smp_mb__(?:before|after)_atomic
?

On Sun, Jan 10, 2016 at 07:07:05AM -0800, Joe Perches wrote:

On Sun, 2016-01-10 at 13:56 +0200, Michael S. Tsirkin wrote:

quoted

SMP-only barriers were missing in checkpatch.pl

Refactor code slightly to make adding more variants easier.

[]

quoted

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl

[]

quoted

@@ -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;

Yes but virt barriers (added in patch 3) are same things but prefixed
with virt_.  So we need the stems without smp_ prefix. If smp_barriers is
too confusing we'll just need to give them some other name.
How about:
my $smp_barrier_stems

?

quoted

+		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;		

quoted

+
+		if ($line =~ /\b($all_barriers)\s*\(/) {

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

quoted

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

On Sun, Jan 10, 2016 at 07:17:31AM -0800, Joe Perches wrote:

On Sun, 2016-01-10 at 07:07 -0800, Joe Perches wrote:

quoted

On Sun, 2016-01-10 at 13:56 +0200, Michael S. Tsirkin wrote:

quoted

SMP-only barriers were missing in checkpatch.pl

Refactor code slightly to make adding more variants easier.

[]

quoted

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl

[]

quoted

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

That's missing (?:barriers) too.

My version has it but need to add ?: to avoid
a capture group.

btw: shouldn't this also have
	smp_mb__(?:before|after)_atomic
?

Good catch, included in the next version.

-- 
MST