futex: Correct futex_q woken state commentary

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>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dinakar Guniguntala <dino@in.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20090922053029.8717.62798.stgit@Aeon>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/futex.c b/kernel/futex.c
index 720fa3dd629de25cbfdac3ec9b270464e2787388..f92afbe3d3a14c1cd3e867013c67203c21e226a1 100644 (file)
--- 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;
 };