Re: 2.6.0-test3-mm1: scheduling while atomic (ext3?)

[Andrew Morton <akpm@osdl.org>]

Jurriaan on adsl-gate <thunder7@xs4all.nl> wrote:
>
> > Exactly what sort of CPU are you using?
>  > -
>  AMD Athlon XP2400+ on a VIA KT400 chipset, single CPU-system.

OK, thanks.  The word is that Athlons will, very occasionally,
take a fault when prefetching from an unmapped address.

 include/linux/list.h |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff -puN include/linux/list.h~hlist_for_each-fix include/linux/list.h
--- 25/include/linux/list.h~hlist_for_each-fix	2003-08-13 02:29:32.000000000 -0700
+++ 25-akpm/include/linux/list.h	2003-08-13 02:37:33.000000000 -0700
@@ -504,11 +504,15 @@ static __inline__ void hlist_add_after(s
 
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
-/* Cannot easily do prefetch unfortunately */
-#define hlist_for_each(pos, head) \
-	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
-	     pos = pos->next) 
+#define hlist_for_each(pos, head)					\
+	for (	pos = (head)->first;					\
+		likely(pos) && ({					\
+				if (likely(pos->next))			\
+					prefetch(pos->next);		\
+				1; });					\
+		pos = pos->next)
 
+/* Cannot easily do prefetch unfortunately */
 #define hlist_for_each_safe(pos, n, head) \
 	for (pos = (head)->first; n = pos ? pos->next : 0, pos; \
 	     pos = n)

_