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 <mpatocka@xxxxxxxxxx>
---
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 2018-04-16 21:10:05.000000000 +0200
+++ linux-2.6/kernel/sched/swait.c 2018-04-16 21:10:05.000000000 +0200
@@ -75,6 +75,7 @@ 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)
{
@@ -104,6 +105,7 @@ 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)
{
--
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