Merge tag 'locking-urgent-2026-05-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fix from Ingo Molnar:
 "Fix lockup in requeue-PI during signal/timeout wakeups, by Sebastian
  Andrzej Siewior"

* tag 'locking-urgent-2026-05-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Prevent lockup in requeue-PI during signal/ timeout wakeup

Author: torvalds

kernel/futex/requeue.c

@@ -319,8 +319,11 @@ futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
 		return -EINVAL;
 
 	/* Ensure that this does not race against an early wakeup */
-	if (!futex_requeue_pi_prepare(top_waiter, NULL))
+	if (!futex_requeue_pi_prepare(top_waiter, NULL)) {
+		plist_del(&top_waiter->list, &hb1->chain);
+		futex_hb_waiters_dec(hb1);
 		return -EAGAIN;
+	}
 
 	/*
 	 * Try to take the lock for top_waiter and set the FUTEX_WAITERS bit
@@ -722,10 +725,12 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
 
 	/*
 	 * We were woken prior to requeue by a timeout or a signal.
-	 * Unqueue the futex_q and determine which it was.
+	 * Conditionally unqueue the futex_q and determine which it was.
 	 */
-	plist_del(&q->list, &hb->chain);
-	futex_hb_waiters_dec(hb);
+	if (!plist_node_empty(&q->list)) {
+		plist_del(&q->list, &hb->chain);
+		futex_hb_waiters_dec(hb);
+	}
 
 	/* Handle spurious wakeups gracefully */
 	ret = -EWOULDBLOCK;