[patch V4 63/68] futex: Simplify handle_early_requeue_pi_wakeup()

Thomas Gleixner
2021-08-11T12:26:11Z

Move the futex key match out of handle_early_requeue_pi_wakeup() which
allows to simplify that function. The upcoming state machine for
requeue_pi() will make that go away.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: New patch - Suggested by Peter
---
kernel/futex.c | 50 +++++++++++++++++++++++---------------------------
1 file changed, 23 insertions(+), 27 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3070,27 +3070,22 @@ static int futex_unlock_pi(u32 __user *u
}

/**
- * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex
+ * handle_early_requeue_pi_wakeup() - Handle early wakeup on the initial futex
* @hb: the hash_bucket futex_q was original enqueued on
* @q: the futex_q woken while waiting to be requeued
- * @key2: the futex_key of the requeue target futex
* @timeout: the timeout associated with the wait (NULL if none)
*
- * Detect if the task was woken on the initial futex as opposed to the requeue
- * target futex. If so, determine if it was a timeout or a signal that caused
- * the wakeup and return the appropriate error code to the caller. Must be
- * called with the hb lock held.
+ * Determine the cause for the early wakeup.
*
* Return:
- * - 0 = no early wakeup detected;
- * - <0 = -ETIMEDOUT or -ERESTARTNOINTR
+ * -EWOULDBLOCK or -ETIMEDOUT or -ERESTARTNOINTR
*/
static inline
int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
- struct futex_q *q, union futex_key *key2,
+ struct futex_q *q,
struct hrtimer_sleeper *timeout)
{
- int ret = 0;
+ int ret;

/*
* With the hb lock held, we avoid races while we process the wakeup.
@@ -3099,22 +3094,21 @@ int handle_early_requeue_pi_wakeup(struc
* It can't be requeued from uaddr2 to something else since we don't
* support a PI aware source futex for requeue.
*/
- if (!match_futex(&q->key, key2)) {
- WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr));
- /*
- * We were woken prior to requeue by a timeout or a signal.
- * Unqueue the futex_q and determine which it was.
- */
- plist_del(&q->list, &hb->chain);
- hb_waiters_dec(hb);
-
- /* Handle spurious wakeups gracefully */
- ret = -EWOULDBLOCK;
- if (timeout && !timeout->task)
- ret = -ETIMEDOUT;
- else if (signal_pending(current))
- ret = -ERESTARTNOINTR;
- }
+ WARN_ON_ONCE(&hb->lock != q->lock_ptr);
+
+ /*
+ * We were woken prior to requeue by a timeout or a signal.
+ * Unqueue the futex_q and determine which it was.
+ */
+ plist_del(&q->list, &hb->chain);
+ hb_waiters_dec(hb);
+
+ /* Handle spurious wakeups gracefully */
+ ret = -EWOULDBLOCK;
+ if (timeout && !timeout->task)
+ ret = -ETIMEDOUT;
+ else if (signal_pending(current))
+ ret = -ERESTARTNOINTR;
return ret;
}

@@ -3217,7 +3211,9 @@ static int futex_wait_requeue_pi(u32 __u
futex_wait_queue_me(hb, &q, to);

spin_lock(&hb->lock);
- ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
+ /* Is @q still queued on uaddr1? */
+ if (!match_futex(&q->key, key2))
+ ret = handle_early_requeue_pi_wakeup(hb, &q, to);
spin_unlock(&hb->lock);
if (ret)
goto out;