[patch V3 15/20] sched/swait: Prepare usage in completions

Thomas Gleixner
2020-03-21T11:37:37Z

From: Thomas Gleixner <tglx@linutronix.de>

As a preparation to use simple wait queues for completions:

- Provide swake_up_all_locked() to support complete_all()
- Make __prepare_to_swait() public available

This is done to enable the usage of complete() within truly atomic contexts
on a PREEMPT_RT enabled kernel.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
V2: Add comment to swake_up_all_locked()
---
kernel/sched/sched.h | 3 +++
kernel/sched/swait.c | 15 ++++++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2492,3 +2492,6 @@ static inline bool is_per_cpu_kthread(st
return true;
}
#endif
+
+void swake_up_all_locked(struct swait_queue_head *q);
+void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
--- a/kernel/sched/swait.c
+++ b/kernel/sched/swait.c
@@ -32,6 +32,19 @@ void swake_up_locked(struct swait_queue_
}
EXPORT_SYMBOL(swake_up_locked);

+/*
+ * Wake up all waiters. This is an interface which is solely exposed for
+ * completions and not for general usage.
+ *
+ * It is intentionally different from swake_up_all() to allow usage from
+ * hard interrupt context and interrupt disabled regions.
+ */
+void swake_up_all_locked(struct swait_queue_head *q)
+{
+ while (!list_empty(&q->task_list))
+ swake_up_locked(q);
+}
+
void swake_up_one(struct swait_queue_head *q)
{
unsigned long flags;
@@ -69,7 +82,7 @@ void swake_up_all(struct swait_queue_hea
}
EXPORT_SYMBOL(swake_up_all);

-static void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
+void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
{
wait->task = current;
if (list_empty(&wait->task_list))