Commit 781f7fd9 authored by Huang Ying's avatar Huang Ying Committed by Ingo Molnar
Browse files

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



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: default avatarHuang Ying <ying.huang@intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@elte.hu>
parent a3127336

include/linux/llist.h

+5 −1
Original line number Diff line number Diff line
@@ -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;

}



/**

lib/llist.c

+5 −1
Original line number Diff line number Diff line
@@ -34,8 +34,10 @@ 
 * @new_first:	first entry in batch to be added

 * @new_last:	last entry in batch to be added

 * @head:	the head for your lock-less list

 *

 * Return whether list is empty before adding.

 */

void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,

bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,

		     struct llist_head *head)

{

	struct llist_node *entry, *old_entry;
@@ -49,6 +51,8 @@ void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, 
			break;

		cpu_relax();

	}



	return old_entry == NULL;

}

EXPORT_SYMBOL_GPL(llist_add_batch);

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