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llist: Return whether list is empty before adding in llist_add()

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Extend the llist_add*() functions to return a success indicator, this
allows us in the scheduler code to send an IPI if the queue was empty.

( There's no effect on existing users, because the list_add_xxx() functions
  are inline, thus this will be optimized out by the compiler if not used
  by callers. )

Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315461646-1379-5-git-send-email-ying.huang@intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Huang Ying
2011-09-08 14:00:45 +08:00
committed by Ingo Molnar
parent a3127336b7
commit 781f7fd916
2 changed files with 10 additions and 2 deletions
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6
include/linux/llist.h
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@@ -142,8 +142,10 @@ static inline bool llist_empty(const struct llist_head *head)
* llist_add - add a new entry
* @new: new entry to be added
* @head: the head for your lock-less list
*
* Return whether list is empty before adding.
*/
static inline void llist_add(struct llist_node *new, struct llist_head *head)
static inline bool llist_add(struct llist_node *new, struct llist_head *head)
{
struct llist_node *entry, *old_entry;
@@ -156,6 +158,8 @@ static inline void llist_add(struct llist_node *new, struct llist_head *head)
break;
cpu_relax();
}
return old_entry == NULL;
}
/**