In order to reduce locking overhead, I use the spinlock in swait_queue_head to protect not only the wait queue, but also the list of events. Consequently, I need to use unlocked functions __prepare_to_swait and __finish_swait. These functions are declared in the file include/linux/swait.h, but they are not exported, and so they are not useable from kernel modules.
Signed-off-by: Mikulas Patocka <[email protected]> --- kernel/sched/swait.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6/kernel/sched/swait.c =================================================================== --- linux-2.6.orig/kernel/sched/swait.c +++ linux-2.6/kernel/sched/swait.c @@ -72,6 +72,7 @@ void __prepare_to_swait(struct swait_que if (list_empty(&wait->task_list)) list_add(&wait->task_list, &q->task_list); } +EXPORT_SYMBOL(__prepare_to_swait); void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state) { @@ -101,6 +102,7 @@ void __finish_swait(struct swait_queue_h if (!list_empty(&wait->task_list)) list_del_init(&wait->task_list); } +EXPORT_SYMBOL(__finish_swait); void finish_swait(struct swait_queue_head *q, struct swait_queue *wait) {
