linux-kernel - [PATCH 3/4] kernel/futex: Move hb unlock out of unqueue_me

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Message-Id: <20210226175029.50335-3-dave@stgolabs.net>
Date:   Fri, 26 Feb 2021 09:50:28 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     tglx@...utronix.de
Cc:     mingo@...hat.com, peterz@...radead.org, dvhart@...radead.org,
        dave@...olabs.net, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 3/4] kernel/futex: Move hb unlock out of unqueue_me_pi()

This improves the code readability, and the locking more obvious
as it becomes symmetric for the caller.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 kernel/futex.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index ee09995d707b..dcd6132485e1 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2318,19 +2318,15 @@ static int unqueue_me(struct futex_q *q)
 
 /*
  * PI futexes can not be requeued and must remove themself from the
- * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
- * and dropped here.
+ * hash bucket. The hash bucket lock (i.e. lock_ptr) is held.
  */
 static void unqueue_me_pi(struct futex_q *q)
-	__releases(q->lock_ptr)
 {
 	__unqueue_futex(q);
 
 	BUG_ON(!q->pi_state);
 	put_pi_state(q->pi_state);
 	q->pi_state = NULL;
-
-	spin_unlock(q->lock_ptr);
 }
 
 static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
@@ -2913,8 +2909,8 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
 	if (res)
 		ret = (res < 0) ? res : 0;
 
-	/* Unqueue and drop the lock */
 	unqueue_me_pi(&q);
+	spin_unlock(q.lock_ptr);
 	goto out;
 
 out_unlock_put_key:
@@ -3290,8 +3286,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		if (res)
 			ret = (res < 0) ? res : 0;
 
-		/* Unqueue and drop the lock. */
 		unqueue_me_pi(&q);
+		spin_unlock(q.lock_ptr);
 	}
 
 	if (ret == -EINTR) {
-- 
2.26.2