[PATCH 1/3] plist: pass the real plist_head to plist_del()

Lai Jiangshan
2010-12-16T10:22:21Z

These patches shrink the struct plist_head. After it is shrinked
plist_del() required a real plist_head passed into.

My tests did not cover all paths.

Subject: plist: pass the real plist_head to plist_del()

Some plist_del()s in kernel/futex.c are passed a faked plist_head.

It can work because current code does not require real plist_head
in plist_del(). But it is an undocumented usage, it is not good.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/futex.c b/kernel/futex.c
index 6c683b3..6c4f67a 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -158,6 +158,15 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2)
}

/*
+ * find the bucket of a futex entry.
+ * the same as hash_futex(&q->key) but a little more effcient
+ */
+static struct futex_hash_bucket *futex_bucket(struct futex_q *q)
+{
+ return container_of(q->lock_ptr, struct futex_hash_bucket, lock);
+}
+
+/*
* Take a reference to the resource addressed by a key.
* Can be called while holding spinlocks.
*
@@ -744,7 +753,7 @@ static void wake_futex(struct futex_q *q)
*/
get_task_struct(p);

- plist_del(&q->list, &q->list.plist);
+ plist_del(&q->list, &futex_bucket(q)->chain);
/*
* The waiting task can free the futex_q as soon as
* q->lock_ptr = NULL is written, without taking any locks. A
@@ -1053,7 +1062,7 @@ void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
q->key = *key;

WARN_ON(plist_node_empty(&q->list));
- plist_del(&q->list, &q->list.plist);
+ plist_del(&q->list, &futex_bucket(q)->chain);

WARN_ON(!q->rt_waiter);
q->rt_waiter = NULL;
@@ -1457,7 +1466,7 @@ retry:
goto retry;
}
WARN_ON(plist_node_empty(&q->list));
- plist_del(&q->list, &q->list.plist);
+ plist_del(&q->list, &futex_bucket(q)->chain);

BUG_ON(q->pi_state);

@@ -1478,7 +1487,7 @@ static void unqueue_me_pi(struct futex_q *q)
__releases(q->lock_ptr)
{
WARN_ON(plist_node_empty(&q->list));
- plist_del(&q->list, &q->list.plist);
+ plist_del(&q->list, &futex_bucket(q)->chain);

BUG_ON(!q->pi_state);
free_pi_state(q->pi_state);
@@ -2145,7 +2154,7 @@ 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.
*/
- plist_del(&q->list, &q->list.plist);
+ plist_del(&q->list, &hb->chain);

/* Handle spurious wakeups gracefully */
ret = -EWOULDBLOCK;