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| author | Huang Ying <ying.huang@intel.com> | 2011-09-08 14:00:45 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-10-04 12:43:44 +0200 |
| commit | 781f7fd916fc77a862e20063ed3aeedf173234f9 (patch) | |
| tree | 86d6e89060c765cbab65b7c3e77884d3e7c17e70 | |
| parent | a3127336b71f6833d1483c856dce91fe558dc3a9 (diff) | |
| download | lwn-781f7fd916fc77a862e20063ed3aeedf173234f9.tar.gz lwn-781f7fd916fc77a862e20063ed3aeedf173234f9.zip | |
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>
| -rw-r--r-- | include/linux/llist.h | 6 | ||||
| -rw-r--r-- | lib/llist.c | 6 |
2 files changed, 10 insertions, 2 deletions
diff --git a/include/linux/llist.h b/include/linux/llist.h index ca91875286bf..27bbdf5ddf82 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -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; } /** diff --git a/lib/llist.c b/lib/llist.c index 6c69f1d14c4b..878985c4d19d 100644 --- a/lib/llist.c +++ b/lib/llist.c @@ -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); |