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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: 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>
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@ -142,8 +142,10 @@ static inline bool llist_empty(const struct llist_head *head)
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* llist_add - add a new entry
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* @new: new entry to be added
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* @head: the head for your lock-less list
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*
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* Return whether list is empty before adding.
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*/
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static inline void llist_add(struct llist_node *new, struct llist_head *head)
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static inline bool llist_add(struct llist_node *new, struct llist_head *head)
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{
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struct llist_node *entry, *old_entry;
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@ -156,6 +158,8 @@ static inline void llist_add(struct llist_node *new, struct llist_head *head)
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break;
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cpu_relax();
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}
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return old_entry == NULL;
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}
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/**
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@ -34,8 +34,10 @@
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* @new_first: first entry in batch to be added
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* @new_last: last entry in batch to be added
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* @head: the head for your lock-less list
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*
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* Return whether list is empty before adding.
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*/
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void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
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bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
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struct llist_head *head)
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{
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struct llist_node *entry, *old_entry;
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@ -49,6 +51,8 @@ void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
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break;
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cpu_relax();
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}
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return old_entry == NULL;
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}
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EXPORT_SYMBOL_GPL(llist_add_batch);
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