[PATCH v3 0/3] checkpatch: handling of memory barriers

[PATCH v3 0/3] checkpatch: handling of memory barriers

[Michael S. Tsirkin]

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

This replaces the checkpatch patches in my series
	arch: barrier cleanup + barriers for virt
and will be included in the next version of the series.

changes from v2:
	address comments by Joe Perches:
	use (?: ... ) to avoid unnecessary capture groups
	rename smp_barriers to smp_barrier_stems for clarity
	add barriers before/after atomic
Changes from v1:
	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 | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

-- 
MST

[PATCH v3 1/3] checkpatch.pl: add missing memory barriers

[Michael S. Tsirkin]

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 | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 2b3c228..1c01b7d 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5116,7 +5116,27 @@ 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 $smp_barrier_stems = qr{
+			mb__before_atomic|
+			mb__after_atomic|
+			store_release|
+			load_acquire|
+			store_mb|
+			(?:$barriers)
+		}x;
+		my $all_barriers = qr{
+			$barriers|
+			smp_(?:$smp_barrier_stems)
+		}x;
+
+		if ($line =~ /\b(?:$all_barriers)\s*\(/) {
 			if (!ctx_has_comment($first_line, $linenr)) {
 				WARN("MEMORY_BARRIER",
 				     "memory barrier without comment\n" . $herecurr);
-- 
MST

[PATCH v3 2/3] checkpatch: check for __smp outside barrier.h

[Michael S. Tsirkin]

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@arm.linux.org.uk>
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 1c01b7d..15cfca4 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5143,6 +5143,16 @@ sub process {
 			}
 		}
 
+		my $underscore_smp_barriers = qr{__smp_(?:$smp_barrier_stems)}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

[PATCH v3 3/3] checkpatch: add virt barriers

[Michael S. Tsirkin]

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 15cfca4..4466579 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5133,7 +5133,8 @@ sub process {
 		}x;
 		my $all_barriers = qr{
 			$barriers|
-			smp_(?:$smp_barrier_stems)
+			smp_(?:$smp_barrier_stems)|
+			virt_(?:$smp_barrier_stems)
 		}x;
 
 		if ($line =~ /\b(?:$all_barriers)\s*\(/) {
-- 
MST

Re: [PATCH v3 3/3] checkpatch: add virt barriers

[Julian Calaby]

Hi Michael,

On Mon, Jan 11, 2016 at 6:31 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> 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 15cfca4..4466579 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -5133,7 +5133,8 @@ sub process {
>                 }x;
>                 my $all_barriers = qr{
>                         $barriers|
> -                       smp_(?:$smp_barrier_stems)
> +                       smp_(?:$smp_barrier_stems)|
> +                       virt_(?:$smp_barrier_stems)

Sorry I'm late to the party here, but would it make sense to write this as:

(?:smp|virt)_(?:$smp_barrier_stems)

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/

Re: [PATCH v3 3/3] checkpatch: add virt barriers

[Joe Perches]

On Mon, 2016-01-11 at 09:13 +1100, Julian Calaby wrote:
> On Mon, Jan 11, 2016 at 6:31 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > Add virt_ barriers to list of barriers to check for
> > presence of a comment.
[]
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > @@ -5133,7 +5133,8 @@ sub process {
> >                 }x;
> >                 my $all_barriers = qr{
> >                         $barriers|
> > -                       smp_(?:$smp_barrier_stems)
> > +                       smp_(?:$smp_barrier_stems)|
> > +                       virt_(?:$smp_barrier_stems)
> 
> Sorry I'm late to the party here, but would it make sense to write this as:
> 
> (?:smp|virt)_(?:$smp_barrier_stems)

Yes.  Perhaps the name might be better as barrier_stems.

Also, ideally this would be longest match first or use \b
after the matches so that $all_barriers could work
successfully without a following \s*\(

my $all_barriers = qr{
	(?:smp|virt)_(?:barrier_stems)|
	$barriers)
}x;

or maybe add separate $smp_barriers and $virt_barriers

<shrug>  it doesn't matter much in any case

Re: [PATCH v3 3/3] checkpatch: add virt barriers

[Michael S. Tsirkin]

On Sun, Jan 10, 2016 at 02:52:16PM -0800, Joe Perches wrote:
> On Mon, 2016-01-11 at 09:13 +1100, Julian Calaby wrote:
> > On Mon, Jan 11, 2016 at 6:31 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > Add virt_ barriers to list of barriers to check for
> > > presence of a comment.
> []
> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
> > > @@ -5133,7 +5133,8 @@ sub process {
> > >                 }x;
> > >                 my $all_barriers = qr{
> > >                         $barriers|
> > > -                       smp_(?:$smp_barrier_stems)
> > > +                       smp_(?:$smp_barrier_stems)|
> > > +                       virt_(?:$smp_barrier_stems)
> > 
> > Sorry I'm late to the party here, but would it make sense to write this as:
> > 
> > (?:smp|virt)_(?:$smp_barrier_stems)
> 
> Yes.  Perhaps the name might be better as barrier_stems.
> 
> Also, ideally this would be longest match first or use \b
> after the matches so that $all_barriers could work
> successfully without a following \s*\(
> 
> my $all_barriers = qr{
> 	(?:smp|virt)_(?:barrier_stems)|
> 	$barriers)
> }x;
> 
> or maybe add separate $smp_barriers and $virt_barriers
> 
> <shrug>  it doesn't matter much in any case

OK just to clarify - are you OK with merging the patch as is?
Refactorings can come as patches on top if required.

-- 
MST

Re: [PATCH v3 3/3] checkpatch: add virt barriers

[Julian Calaby]

Hi Michael,

On Mon, Jan 11, 2016 at 9:35 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Sun, Jan 10, 2016 at 02:52:16PM -0800, Joe Perches wrote:
>> On Mon, 2016-01-11 at 09:13 +1100, Julian Calaby wrote:
>> > On Mon, Jan 11, 2016 at 6:31 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
>> > > Add virt_ barriers to list of barriers to check for
>> > > presence of a comment.
>> []
>> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>> []
>> > > @@ -5133,7 +5133,8 @@ sub process {
>> > >                 }x;
>> > >                 my $all_barriers = qr{
>> > >                         $barriers|
>> > > -                       smp_(?:$smp_barrier_stems)
>> > > +                       smp_(?:$smp_barrier_stems)|
>> > > +                       virt_(?:$smp_barrier_stems)
>> >
>> > Sorry I'm late to the party here, but would it make sense to write this as:
>> >
>> > (?:smp|virt)_(?:$smp_barrier_stems)
>>
>> Yes.  Perhaps the name might be better as barrier_stems.
>>
>> Also, ideally this would be longest match first or use \b
>> after the matches so that $all_barriers could work
>> successfully without a following \s*\(
>>
>> my $all_barriers = qr{
>>       (?:smp|virt)_(?:barrier_stems)|
>>       $barriers)
>> }x;
>>
>> or maybe add separate $smp_barriers and $virt_barriers
>>
>> <shrug>  it doesn't matter much in any case
>
> OK just to clarify - are you OK with merging the patch as is?
> Refactorings can come as patches on top if required.

I don't really care either way, I was just asking if it was possible.
If you don't see any value in that change, then don't make it.

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/

Re: [PATCH v3 3/3] checkpatch: add virt barriers

[Michael S. Tsirkin]

On Mon, Jan 11, 2016 at 09:40:18PM +1100, Julian Calaby wrote:
> Hi Michael,
> 
> On Mon, Jan 11, 2016 at 9:35 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Sun, Jan 10, 2016 at 02:52:16PM -0800, Joe Perches wrote:
> >> On Mon, 2016-01-11 at 09:13 +1100, Julian Calaby wrote:
> >> > On Mon, Jan 11, 2016 at 6:31 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >> > > Add virt_ barriers to list of barriers to check for
> >> > > presence of a comment.
> >> []
> >> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> >> []
> >> > > @@ -5133,7 +5133,8 @@ sub process {
> >> > >                 }x;
> >> > >                 my $all_barriers = qr{
> >> > >                         $barriers|
> >> > > -                       smp_(?:$smp_barrier_stems)
> >> > > +                       smp_(?:$smp_barrier_stems)|
> >> > > +                       virt_(?:$smp_barrier_stems)
> >> >
> >> > Sorry I'm late to the party here, but would it make sense to write this as:
> >> >
> >> > (?:smp|virt)_(?:$smp_barrier_stems)
> >>
> >> Yes.  Perhaps the name might be better as barrier_stems.
> >>
> >> Also, ideally this would be longest match first or use \b
> >> after the matches so that $all_barriers could work
> >> successfully without a following \s*\(
> >>
> >> my $all_barriers = qr{
> >>       (?:smp|virt)_(?:barrier_stems)|
> >>       $barriers)
> >> }x;
> >>
> >> or maybe add separate $smp_barriers and $virt_barriers
> >>
> >> <shrug>  it doesn't matter much in any case
> >
> > OK just to clarify - are you OK with merging the patch as is?
> > Refactorings can come as patches on top if required.
> 
> I don't really care either way, I was just asking if it was possible.
> If you don't see any value in that change, then don't make it.
> 
> Thanks,
> 
> -- 
> Julian Calaby
> 
> Email: julian.calaby@gmail.com
> Profile: http://www.google.com/profiles/julian.calaby/

OK, got it, thanks.

I will rename smp_barrier_stems to barrier_stems since
this doesn't need too much testing.

I'd rather keep the regex code as is since changing it requires
testing.  I might play with it some more in the future
but I'd like to merge it in the current form to help make
sure __smp barriers are not misused.

I'll post v4 now - an ack will be appreciated.
-- 
MST