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Commit 2c675598 authored by Nick Piggin's avatar Nick Piggin Committed by Nick Piggin
Browse files

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: default avatarNick Piggin <npiggin@kernel.dk>
parent 90dbb77b

include/linux/list_bl.h

+3 −2
Original line number Diff line number Diff line
@@ -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);

}

include/linux/rculist_bl.h

+2 −1
Original line number Diff line number Diff line
@@ -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));

}