[PATCH v2 0/3] checkpatch: handling of memory barriers

[PATCH v2 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 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

[PATCH v2 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 | 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

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

[Joe Perches]

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);

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

[Joe Perches]

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:
> > 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
[]
> 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
?

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

[Michael S. Tsirkin]

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:
> > 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
> []
> > 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

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

[Michael S. Tsirkin]

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:
> > 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;
> 

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

?

> > +		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);

[PATCH v2 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 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

Re: [PATCH v2 2/3] checkpatch: check for __smp outside barrier.h

[Joe Perches]

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)) {

[PATCH v2 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 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