On Thu, 29 Aug 2013 15:24:46 +0400 Maxim Patlasov <mpatlasov@xxxxxxxxxxxxx> wrote:
> Hi Stephen,
>
> 08/29/2013 01:47 PM, Stephen Rothwell __________:
> > Hi Andrew,
> >
> > After merging the akpm tree, today's linux-next build (sparc64 defconfig
> > and others) produced these warnings:
> >
> > mm/page-writeback.c: In function 'balance_dirty_pages_ratelimited':
> > mm/page-writeback.c:1450:13: warning: 'bdi_thresh' may be used uninitialized in this function [-Wuninitialized]
> > mm/page-writeback.c:1372:16: note: 'bdi_thresh' was declared here
> > mm/page-writeback.c:1226:16: warning: 'bdi_dirty' may be used uninitialized in this function [-Wuninitialized]
> > mm/page-writeback.c:1369:16: note: 'bdi_dirty' was declared here
> >
> > Possibly introduced by commit 34c547af1e23 ("mm/page-writeback.c: add
> > strictlimit feature"), but I am not sure anything can be done about them.
> >
>
> This looks as gcc glitch. So far as I didn't observe the warnings, the
> version of gcc does matter. May be moving the definitions of the two
> variables into for(;;){...} would help. Could you please give it a try?
Shuffling the definitions around won't help. To fix this we'll need to
add more code and I hate adding runtime overhead to address
compile-time issues. So...
--- a/mm/page-writeback.c~a
+++ a/mm/page-writeback.c
@@ -1366,10 +1366,8 @@ static void balance_dirty_pages(struct a
{
unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
- unsigned long bdi_dirty;
unsigned long background_thresh;
unsigned long dirty_thresh;
- unsigned long bdi_thresh;
long period;
long pause;
long max_pause;
@@ -1385,8 +1383,10 @@ static void balance_dirty_pages(struct a
for (;;) {
unsigned long now = jiffies;
- unsigned long dirty;
+ unsigned long uninitialized_var(bdi_thresh);
unsigned long thresh;
+ unsigned long uninitialized_var(bdi_dirty);
+ unsigned long dirty;
unsigned long bg_thresh;
/*
_
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