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Commit d8d88fbb authored by Darren Hart's avatar Darren Hart Committed by Ingo Molnar
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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: default avatarDarren Hart <dvhltc@us.ibm.com>
Acked-by: default avatarPeter 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: default avatarIngo Molnar <mingo@elte.hu>
parent d96ee56c
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+16 −16
Original line number Diff line number Diff line
@@ -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;
};