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fs: hlist UP debug fixup 

Po-Yu Chuang <ratbert.chuang@gmail.com> noticed that hlist_bl_set_first could
crash on a UP system when LIST_BL_LOCKMASK is 0, because

	LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));

always evaulates to true.

Fix the expression, and also avoid a dependency between bit spinlock
implementation and list bl code (list code shouldn't know anything
except that bit 0 is set when adding and removing elements). Eventually
if a good use case comes up, we might use this list to store 1 or more
arbitrary bits of data, so it really shouldn't be tied to locking either,
but for now they are helpful for debugging.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-14 02:36:43 +00:00 committed by Nick Piggin
parent 90dbb77ba4
commit 2c6755988a
2 changed files with 5 additions and 3 deletions
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5
include/linux/list_bl.h
View File

@ -16,7 +16,7 @@
* some fast and compact auxiliary data.
*/
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
#if defined(CONFIG_SMP)
#define LIST_BL_LOCKMASK 1UL
#else
#define LIST_BL_LOCKMASK 0UL
@ -62,7 +62,8 @@ static inline void hlist_bl_set_first(struct hlist_bl_head *h,
struct hlist_bl_node *n)
{
LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
LIST_BL_LOCKMASK);
h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
}

3
include/linux/rculist_bl.h
View File

@ -11,7 +11,8 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
struct hlist_bl_node *n)
{
LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
LIST_BL_LOCKMASK);
rcu_assign_pointer(h->first,
(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
}