aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorHuang Ying <ying.huang@intel.com>2011-09-08 14:00:45 +0800
committerIngo Molnar <mingo@elte.hu>2011-10-04 12:43:44 +0200
commit781f7fd916fc77a862e20063ed3aeedf173234f9 (patch)
tree86d6e89060c765cbab65b7c3e77884d3e7c17e70
parenta3127336b71f6833d1483c856dce91fe558dc3a9 (diff)
downloadlinux-linaro-stable-781f7fd916fc77a862e20063ed3aeedf173234f9.tar.gz
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.h6
-rw-r--r--lib/llist.c6
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);