* [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized
@ 2014-09-10 6:12 Xiubo Li
2014-09-10 18:50 ` David Rientjes
0 siblings, 1 reply; 5+ messages in thread
From: Xiubo Li @ 2014-09-10 6:12 UTC (permalink / raw)
To: akpm, vbabka, mgorman, rientjes, minchan, linux-mm; +Cc: Xiubo Li
C mm/compaction.o
mm/compaction.c: In function isolate_freepages_block:
mm/compaction.c:364:37: warning: flags may be used uninitialized in
this function [-Wmaybe-uninitialized]
&& compact_unlock_should_abort(&cc->zone->lock, flags,
^
In file included from include/linux/irqflags.h:15:0,
from ./arch/arm/include/asm/bitops.h:27,
from include/linux/bitops.h:33,
from include/linux/kernel.h:10,
from include/linux/list.h:8,
from include/linux/preempt.h:10,
from include/linux/spinlock.h:50,
from include/linux/swap.h:4,
from mm/compaction.c:10:
mm/compaction.c: In function isolate_migratepages_block:
./arch/arm/include/asm/irqflags.h:152:2: warning: flags may be used
uninitialized in this function [-Wmaybe-uninitialized]
asm volatile(
^
mm/compaction.c:576:16: note: flags as declared here
unsigned long flags;
^
Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
---
mm/compaction.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 7d9d92e..fb28d85 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -344,7 +344,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
{
int nr_scanned = 0, total_isolated = 0;
struct page *cursor, *valid_page = NULL;
- unsigned long flags;
+ unsigned long flags = 0;
bool locked = false;
unsigned long blockpfn = *start_pfn;
@@ -573,7 +573,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
unsigned long nr_scanned = 0, nr_isolated = 0;
struct list_head *migratelist = &cc->migratepages;
struct lruvec *lruvec;
- unsigned long flags;
+ unsigned long flags = 0;
bool locked = false;
struct page *page = NULL, *valid_page = NULL;
--
2.1.0.27.g96db324
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^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized
2014-09-10 6:12 [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized Xiubo Li
@ 2014-09-10 18:50 ` David Rientjes
2014-09-11 8:04 ` Michal Hocko
2014-09-11 9:02 ` Arnd Bergmann
0 siblings, 2 replies; 5+ messages in thread
From: David Rientjes @ 2014-09-10 18:50 UTC (permalink / raw)
To: Xiubo Li; +Cc: Andrew Morton, Arnd Bergmann, vbabka, mgorman, minchan, linux-mm
On Wed, 10 Sep 2014, Xiubo Li wrote:
> C mm/compaction.o
> mm/compaction.c: In function isolate_freepages_block:
> mm/compaction.c:364:37: warning: flags may be used uninitialized in
> this function [-Wmaybe-uninitialized]
> && compact_unlock_should_abort(&cc->zone->lock, flags,
> ^
> In file included from include/linux/irqflags.h:15:0,
> from ./arch/arm/include/asm/bitops.h:27,
> from include/linux/bitops.h:33,
> from include/linux/kernel.h:10,
> from include/linux/list.h:8,
> from include/linux/preempt.h:10,
> from include/linux/spinlock.h:50,
> from include/linux/swap.h:4,
> from mm/compaction.c:10:
> mm/compaction.c: In function isolate_migratepages_block:
> ./arch/arm/include/asm/irqflags.h:152:2: warning: flags may be used
> uninitialized in this function [-Wmaybe-uninitialized]
> asm volatile(
> ^
> mm/compaction.c:576:16: note: flags as declared here
> unsigned long flags;
> ^
>
> Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
Arnd Bergmann already sent a patch for this to use uninitialized_var()
privately but it didn't get cc'd to any mailing list, sorry.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized
2014-09-10 18:50 ` David Rientjes
@ 2014-09-11 8:04 ` Michal Hocko
2014-09-11 9:27 ` Li.Xiubo
2014-09-11 9:02 ` Arnd Bergmann
1 sibling, 1 reply; 5+ messages in thread
From: Michal Hocko @ 2014-09-11 8:04 UTC (permalink / raw)
To: David Rientjes
Cc: Xiubo Li, Andrew Morton, Arnd Bergmann, vbabka, mgorman, minchan,
linux-mm
On Wed 10-09-14 11:50:41, David Rientjes wrote:
> On Wed, 10 Sep 2014, Xiubo Li wrote:
>
> > C mm/compaction.o
> > mm/compaction.c: In function isolate_freepages_block:
> > mm/compaction.c:364:37: warning: flags may be used uninitialized in
> > this function [-Wmaybe-uninitialized]
> > && compact_unlock_should_abort(&cc->zone->lock, flags,
> > ^
> > In file included from include/linux/irqflags.h:15:0,
> > from ./arch/arm/include/asm/bitops.h:27,
> > from include/linux/bitops.h:33,
> > from include/linux/kernel.h:10,
> > from include/linux/list.h:8,
> > from include/linux/preempt.h:10,
> > from include/linux/spinlock.h:50,
> > from include/linux/swap.h:4,
> > from mm/compaction.c:10:
> > mm/compaction.c: In function isolate_migratepages_block:
> > ./arch/arm/include/asm/irqflags.h:152:2: warning: flags may be used
> > uninitialized in this function [-Wmaybe-uninitialized]
> > asm volatile(
> > ^
> > mm/compaction.c:576:16: note: flags as declared here
> > unsigned long flags;
> > ^
> >
> > Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
>
> Arnd Bergmann already sent a patch for this to use uninitialized_var()
> privately but it didn't get cc'd to any mailing list, sorry.
Besides that setting flags to 0 is certainly a misleading way to fix
this issue. uninitialized_var is a correct way because the warning is a
false possitive. compact_unlock_should_abort will not touch the flags if
locked is false and this is true only after a lock has been taken and
flags set. (this should be preferably in the patch description).
--
Michal Hocko
SUSE Labs
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^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized
2014-09-11 8:04 ` Michal Hocko
@ 2014-09-11 9:27 ` Li.Xiubo
0 siblings, 0 replies; 5+ messages in thread
From: Li.Xiubo @ 2014-09-11 9:27 UTC (permalink / raw)
To: Michal Hocko, David Rientjes
Cc: Andrew Morton, Arnd Bergmann, vbabka@suse.cz, mgorman@suse.de,
minchan@kernel.org, linux-mm@kvack.org
Hi,
> > Arnd Bergmann already sent a patch for this to use uninitialized_var()
> > privately but it didn't get cc'd to any mailing list, sorry.
>
> Besides that setting flags to 0 is certainly a misleading way to fix
> this issue. uninitialized_var is a correct way because the warning is a
> false possitive. compact_unlock_should_abort will not touch the flags if
> locked is false and this is true only after a lock has been taken and
> flags set. (this should be preferably in the patch description).
>
Yes, right.
This should be added to the commit comment with the patch.
Thanks,
BRs
Xiubo
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized
2014-09-10 18:50 ` David Rientjes
2014-09-11 8:04 ` Michal Hocko
@ 2014-09-11 9:02 ` Arnd Bergmann
1 sibling, 0 replies; 5+ messages in thread
From: Arnd Bergmann @ 2014-09-11 9:02 UTC (permalink / raw)
To: David Rientjes
Cc: Xiubo Li, Andrew Morton, vbabka, mgorman, minchan, linux-mm
On Wednesday 10 September 2014 11:50:41 David Rientjes wrote:
> On Wed, 10 Sep 2014, Xiubo Li wrote:
>
> > C mm/compaction.o
> > mm/compaction.c: In function isolate_freepages_block:
> > mm/compaction.c:364:37: warning: flags may be used uninitialized in
> > this function [-Wmaybe-uninitialized]
> > && compact_unlock_should_abort(&cc->zone->lock, flags,
> > ^
> > In file included from include/linux/irqflags.h:15:0,
> > from ./arch/arm/include/asm/bitops.h:27,
> > from include/linux/bitops.h:33,
> > from include/linux/kernel.h:10,
> > from include/linux/list.h:8,
> > from include/linux/preempt.h:10,
> > from include/linux/spinlock.h:50,
> > from include/linux/swap.h:4,
> > from mm/compaction.c:10:
> > mm/compaction.c: In function isolate_migratepages_block:
> > ./arch/arm/include/asm/irqflags.h:152:2: warning: flags may be used
> > uninitialized in this function [-Wmaybe-uninitialized]
> > asm volatile(
> > ^
> > mm/compaction.c:576:16: note: flags as declared here
> > unsigned long flags;
> > ^
> >
> > Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
>
> Arnd Bergmann already sent a patch for this to use uninitialized_var()
> privately but it didn't get cc'd to any mailing list, sorry.
Oops, I hadn't noticed that I missed the mailing lists, sorry about that.
For reference, see my patch below.
Arnd
8<------
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2014-09-10 6:12 [PATCH] mm/compaction: Fix warning of 'flags' may be used uninitialized Xiubo Li
2014-09-10 18:50 ` David Rientjes
2014-09-11 8:04 ` Michal Hocko
2014-09-11 9:27 ` Li.Xiubo
2014-09-11 9:02 ` Arnd Bergmann
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