linux-kernel - [tip: locking/futex] futex: Pull futex_hash() out of futex_q

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Message-ID: <174670043847.406.10022879751966204246.tip-bot2@tip-bot2>
Date: Thu, 08 May 2025 10:33:58 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/futex] futex: Pull futex_hash() out of futex_q_lock()

The following commit has been merged into the locking/futex branch of tip:

Commit-ID:     2fb292096d950a67a1941949a08a60ddd3193da3
Gitweb:        https://git.kernel.org/tip/2fb292096d950a67a1941949a08a60ddd3193da3
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 16 Apr 2025 18:29:04 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Sat, 03 May 2025 12:02:05 +02:00

futex: Pull futex_hash() out of futex_q_lock()

Getting the hash bucket and queuing it are two distinct actions. In
light of wanting to add a put hash bucket function later, untangle
them.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20250416162921.513656-5-bigeasy@linutronix.de
---
 kernel/futex/core.c     | 7 +------
 kernel/futex/futex.h    | 2 +-
 kernel/futex/pi.c       | 3 ++-
 kernel/futex/waitwake.c | 6 ++++--
 4 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index cca1585..7adc914 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -502,13 +502,9 @@ void __futex_unqueue(struct futex_q *q)
 }
 
 /* The key must be already stored in q->key. */
-struct futex_hash_bucket *futex_q_lock(struct futex_q *q)
+void futex_q_lock(struct futex_q *q, struct futex_hash_bucket *hb)
 	__acquires(&hb->lock)
 {
-	struct futex_hash_bucket *hb;
-
-	hb = futex_hash(&q->key);
-
 	/*
 	 * Increment the counter before taking the lock so that
 	 * a potential waker won't miss a to-be-slept task that is
@@ -522,7 +518,6 @@ struct futex_hash_bucket *futex_q_lock(struct futex_q *q)
 	q->lock_ptr = &hb->lock;
 
 	spin_lock(&hb->lock);
-	return hb;
 }
 
 void futex_q_unlock(struct futex_hash_bucket *hb)
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 16aafd0..a219903 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -354,7 +354,7 @@ static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
 #endif
 }
 
-extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q);
+extern void futex_q_lock(struct futex_q *q, struct futex_hash_bucket *hb);
 extern void futex_q_unlock(struct futex_hash_bucket *hb);
 
 
diff --git a/kernel/futex/pi.c b/kernel/futex/pi.c
index 7a94184..3bf942e 100644
--- a/kernel/futex/pi.c
+++ b/kernel/futex/pi.c
@@ -939,7 +939,8 @@ retry:
 		goto out;
 
 retry_private:
-	hb = futex_q_lock(&q);
+	hb = futex_hash(&q.key);
+	futex_q_lock(&q, hb);
 
 	ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current,
 				   &exiting, 0);
diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index 6cf1070..1108f37 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -441,7 +441,8 @@ retry:
 		struct futex_q *q = &vs[i].q;
 		u32 val = vs[i].w.val;
 
-		hb = futex_q_lock(q);
+		hb = futex_hash(&q->key);
+		futex_q_lock(q, hb);
 		ret = futex_get_value_locked(&uval, uaddr);
 
 		if (!ret && uval == val) {
@@ -611,7 +612,8 @@ retry:
 		return ret;
 
 retry_private:
-	hb = futex_q_lock(q);
+	hb = futex_hash(&q->key);
+	futex_q_lock(q, hb);
 
 	ret = futex_get_value_locked(&uval, uaddr);