[PATCH 4/5] futex: correct futex_q woken state commentary

Darren Hart
2009-09-22T05:30:37Z

Use kernel-doc format to describe struct futex_q. Correct the wakeup
definition to eliminate the statement about waking the waiter between
the plist_del() and the q->lock_ptr = 0. Note in the comment that PI
futexes have a different definition of the woken state.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Dinakar Guniguntala <dino@in.ibm.com>
CC: John Stultz <johnstul@us.ibm.com>
---

kernel/futex.c | 32 ++++++++++++++++----------------
1 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 720fa3d..f92afbe 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -89,36 +89,36 @@ struct futex_pi_state {
union futex_key key;
};

-/*
- * We use this hashed waitqueue instead of a normal wait_queue_t, so
+/**
+ * struct futex_q - The hashed futex queue entry, one per waiting task
+ * @task: the task waiting on the futex
+ * @lock_ptr: the hash bucket lock
+ * @key: the key the futex is hashed on
+ * @pi_state: optional priority inheritance state
+ * @rt_waiter: rt_waiter storage for use with requeue_pi
+ * @requeue_pi_key: the requeue_pi target futex key
+ * @bitset: bitset for the optional bitmasked wakeup
+ *
+ * We use this hashed waitqueue, instead of a normal wait_queue_t, so
* we can wake only the relevant ones (hashed queues may be shared).
*
* A futex_q has a woken state, just like tasks have TASK_RUNNING.
* It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
* The order of wakup is always to make the first condition true, then
- * wake up q->waiter, then make the second condition true.
+ * the second.
+ *
+ * PI futexes are typically woken before they are removed from the hash list via
+ * the rt_mutex code. See unqueue_me_pi().
*/
struct futex_q {
struct plist_node list;
- /* Waiter reference */
- struct task_struct *task;

- /* Which hash list lock to use: */
+ struct task_struct *task;
spinlock_t *lock_ptr;
-
- /* Key which the futex is hashed on: */
union futex_key key;
-
- /* Optional priority inheritance state: */
struct futex_pi_state *pi_state;
-
- /* rt_waiter storage for requeue_pi: */
struct rt_mutex_waiter *rt_waiter;
-
- /* The expected requeue pi target futex key: */
union futex_key *requeue_pi_key;
-
- /* Bitset for the optional bitmasked wakeup */
u32 bitset;
};