Linux Virtualization - Jan 2016 - [PATCH v4 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 replaces the checkpatch patches in my series
	arch: barrier cleanup + barriers for virt
and will be included in the pull request including
the series.

changes from v3:
	rename smp_barrier_stems to barrier_stems
	as suggested by Julian Calaby.
	add (?: ... ) around a variable in regexp,
	in case we change the value later so that it matters.
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

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

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

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 2b3c228..94b4e33 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 $barrier_stems = qr{
+			mb__before_atomic|
+			mb__after_atomic|
+			store_release|
+			load_acquire|
+			store_mb|
+			(?:$barriers)
+		}x;
+		my $all_barriers = qr{
+			(?:$barriers)|
+			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

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 94b4e33..25476c2 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5143,6 +5143,16 @@ sub process {
 			}
 		}
 
+		my $underscore_smp_barriers = qr{__smp_(?:$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

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 25476c2..c7bf1aa 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5133,7 +5133,8 @@ sub process {
 		}x;
 		my $all_barriers = qr{
 			(?:$barriers)|
-			smp_(?:$barrier_stems)
+			smp_(?:$barrier_stems)|
+			virt_(?:$barrier_stems)
 		}x;
 
 		if ($line =~ /\b(?:$all_barriers)\s*\(/) {
-- 
MST

On Mon, Jan 11, 2016 at 12:59:25PM +0200, Michael S. Tsirkin
wrote:
> 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 pull request including
> the series.
> 
> changes from v3:
> 	rename smp_barrier_stems to barrier_stems
> 	as suggested by Julian Calaby.
In fact it was Joe Perches that suggested it.
Sorry about the confusion.
> 	add (?: ... ) around a variable in regexp,
> 	in case we change the value later so that it matters.
> 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
> 
> 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

Hi Michael,

On Mon, Jan 11, 2016 at 10:04 PM, Michael S. Tsirkin <mst at redhat.com>
wrote:
> On Mon, Jan 11, 2016 at 12:59:25PM +0200, Michael S. Tsirkin wrote:
>> 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 pull request including
>> the series.
>>
>> changes from v3:
>>       rename smp_barrier_stems to barrier_stems
>>       as suggested by Julian Calaby.
>
> In fact it was Joe Perches that suggested it.
> Sorry about the confusion.
I was about to point that out.

FWIW this entire series is:

Acked-by: Julian Calaby <julian.calaby at gmail.com>

Thanks,

-- 
Julian Calaby

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

On Mon, 2016-01-11 at 13:00 +0200, Michael S. Tsirkin
wrote:
> As part of memory barrier cleanup, this patchset
> extends checkpatch to make it easier to stop
> incorrect memory barrier usage.
Thanks Michael.

Acked-by: Joe Perches <joe at perches.com>