[PATCH 4/6] futex: add futex wait variant that takes a futex_q directly

[Jens Axboe <axboe@xxxxxxxxx>]

For async trigger of the wait, we need to be able to pass in a futex_q
that is already setup. Add that helper.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 kernel/futex/futex.h    |  3 +++
 kernel/futex/waitwake.c | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 8c12cef83d38..29bf78a1f475 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -156,6 +156,9 @@ extern void __futex_unqueue(struct futex_q *q);
 extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb);
 extern int futex_unqueue(struct futex_q *q);
 
+extern int futex_queue_wait(struct futex_q *q, u32 __user *uaddr,
+			    unsigned int flags, u32 val);
+
 /**
  * futex_queue() - Enqueue the futex_q on the futex_hash_bucket
  * @q:	The futex_q to enqueue
diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index 5151c83e2db8..442dafdfa22a 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -706,3 +706,20 @@ static long futex_wait_restart(struct restart_block *restart)
 				restart->futex.val, tp, restart->futex.bitset);
 }
 
+int futex_queue_wait(struct futex_q *q, u32 __user *uaddr, unsigned int flags,
+		     u32 val)
+{
+	struct futex_hash_bucket *hb;
+	int ret;
+
+	if (!q->bitset)
+		return -EINVAL;
+
+	ret = futex_wait_setup(uaddr, val, flags, q, &hb);
+	if (ret)
+		return ret;
+
+	__futex_queue(q, hb);
+	spin_unlock(&hb->lock);
+	return 0;
+}
-- 
2.39.2