On Thu, 14 Apr 2011 08:41:35 -0700
Dave Hansen <dave@xxxxxxxx> wrote:
> Running sparse on page_alloc.c today, it errors out:
>
> mm/page_alloc.c:96:5: warning: symbol 'percpu_pagelist_fraction' was not declared. Should it be static?
> mm/page_alloc.c:175:5: warning: symbol 'min_free_kbytes' was not declared. Should it be static?
> include/linux/gfp.h:254:17: error: bad constant expression
> include/linux/gfp.h:254:17: error: cannot size expression
>
> which is a line in gfp_zone():
>
> BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
>
> That's really unfortunate, because it ends up hiding all of the other
> legitimate sparse messages (like I introduced with the appended patch):
>
> mm/page_alloc.c:96:5: warning: symbol 'percpu_pagelist_fraction' was not declared. Should it be static?
> mm/page_alloc.c:175:5: warning: symbol 'min_free_kbytes' was not declared. Should it be static?
> mm/page_alloc.c:3692:15: warning: symbol '__early_pfn_to_nid' was not declared. Should it be static?
> mm/page_alloc.c:5315:59: warning: incorrect type in argument 1 (different base types)
> mm/page_alloc.c:5315:59: expected unsigned long [unsigned] [usertype] size
> mm/page_alloc.c:5315:59: got restricted gfp_t [usertype] <noident>
> ...
>
> Is sparse broken, or is that ? Even if it is, should we be working
> around this somehow? It looks like we've basically crippled sparse in
> some spots.
Is sparse having conniptions over that monster expression for
GFP_ZONE_BAD?
The kernel calls gfp_zone() with a constant arg in very few places.
This?
--- a/include/linux/gfp.h~a
+++ a/include/linux/gfp.h
@@ -249,14 +249,9 @@ static inline enum zone_type gfp_zone(gf
z = (GFP_ZONE_TABLE >> (bit * ZONES_SHIFT)) &
((1 << ZONES_SHIFT) - 1);
-
- if (__builtin_constant_p(bit))
- BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
- else {
#ifdef CONFIG_DEBUG_VM
- BUG_ON((GFP_ZONE_BAD >> bit) & 1);
+ BUG_ON((GFP_ZONE_BAD >> bit) & 1);
#endif
- }
return z;
}
_
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