[PATCH v10 03/21] futex: Pull futex_hash() out of futex_q_lock()

From: Sebastian Andrzej Siewior
Date: Wed Mar 12 2025 - 11:16:57 EST


From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
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 cca15859a50be..7adc914878933 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 16aafd0113442..a219903e52084 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 7a941845f7eee..3bf942e9400ac 100644
--- a/kernel/futex/pi.c
+++ b/kernel/futex/pi.c
@@ -939,7 +939,8 @@ int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int tryl
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 6cf10701294b4..1108f373fd315 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -441,7 +441,8 @@ int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *woken)
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 @@ int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
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);

--
2.47.2