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futex: separate futex_wait_queue_me() logic from futex_wait() 

Refactor futex_wait() in preparation for futex_wait_requeue_pi(). In
order to reuse a good chunk of the futex_wait() code for the upcoming
futex_wait_requeue_pi() function, this patch breaks out the
queue-to-wakeup section of futex_wait() into futex_wait_queue_me().

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Darren Hart 2009-04-03 13:39:33 -07:00 committed by Thomas Gleixner
parent 6bb597507f
commit ca5f9524d6
1 changed files with 76 additions and 62 deletions
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138
kernel/futex.c
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@ -1115,24 +1115,87 @@ handle_fault:
static long futex_wait_restart(struct restart_block *restart);
/**
* futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
* @hb: the futex hash bucket, must be locked by the caller
* @q: the futex_q to queue up on
* @timeout: the prepared hrtimer_sleeper, or null for no timeout
* @wait: the wait_queue to add to the futex_q after queueing in the hb
*/
static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
struct hrtimer_sleeper *timeout,
wait_queue_t *wait)
{
queue_me(q, hb);
/*
* There might have been scheduling since the queue_me(), as we
* cannot hold a spinlock across the get_user() in case it
* faults, and we cannot just set TASK_INTERRUPTIBLE state when
* queueing ourselves into the futex hash. This code thus has to
* rely on the futex_wake() code removing us from hash when it
* wakes us up.
*/
/* add_wait_queue is the barrier after __set_current_state. */
__set_current_state(TASK_INTERRUPTIBLE);
/*
* Add current as the futex_q waiter. We don't remove ourselves from
* the wait_queue because we are the only user of it.
*/
add_wait_queue(&q->waiter, wait);
/* Arm the timer */
if (timeout) {
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&timeout->timer))
timeout->task = NULL;
}
/*
* !plist_node_empty() is safe here without any lock.
* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
*/
if (likely(!plist_node_empty(&q->list))) {
/*
* If the timer has already expired, current will already be
* flagged for rescheduling. Only call schedule if there
* is no timeout, or if it has yet to expire.
*/
if (!timeout || timeout->task)
schedule();
}
__set_current_state(TASK_RUNNING);
}
static int futex_wait(u32 __user *uaddr, int fshared,
u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
{
struct task_struct *curr = current;
struct hrtimer_sleeper timeout, *to = NULL;
DECLARE_WAITQUEUE(wait, current);
struct restart_block *restart;
DECLARE_WAITQUEUE(wait, curr);
struct futex_hash_bucket *hb;
struct futex_q q;
u32 uval;
int ret;
struct hrtimer_sleeper t;
int rem = 0;
if (!bitset)
return -EINVAL;
q.pi_state = NULL;
q.bitset = bitset;
if (abs_time) {
to = &timeout;
hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
hrtimer_init_sleeper(to, current);
hrtimer_set_expires_range_ns(&to->timer, *abs_time,
current->timer_slack_ns);
}
retry:
q.key = FUTEX_KEY_INIT;
ret = get_futex_key(uaddr, fshared, &q.key);
@ -1178,75 +1241,22 @@ retry_private:
goto retry;
}
ret = -EWOULDBLOCK;
/* Only actually queue if *uaddr contained val. */
if (unlikely(uval != val)) {
queue_unlock(&q, hb);
goto out_put_key;
}
/* Only actually queue if *uaddr contained val. */
queue_me(&q, hb);
/*
* There might have been scheduling since the queue_me(), as we
* cannot hold a spinlock across the get_user() in case it
* faults, and we cannot just set TASK_INTERRUPTIBLE state when
* queueing ourselves into the futex hash. This code thus has to
* rely on the futex_wake() code removing us from hash when it
* wakes us up.
*/
/* add_wait_queue is the barrier after __set_current_state. */
__set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&q.waiter, &wait);
/*
* !plist_node_empty() is safe here without any lock.
* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
*/
if (likely(!plist_node_empty(&q.list))) {
if (!abs_time)
schedule();
else {
hrtimer_init_on_stack(&t.timer,
clockrt ? CLOCK_REALTIME :
CLOCK_MONOTONIC,
HRTIMER_MODE_ABS);
hrtimer_init_sleeper(&t, current);
hrtimer_set_expires_range_ns(&t.timer, *abs_time,
current->timer_slack_ns);
hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&t.timer))
t.task = NULL;
/*
* the timer could have already expired, in which
* case current would be flagged for rescheduling.
* Don't bother calling schedule.
*/
if (likely(t.task))
schedule();
hrtimer_cancel(&t.timer);
/* Flag if a timeout occured */
rem = (t.task == NULL);
destroy_hrtimer_on_stack(&t.timer);
}
}
__set_current_state(TASK_RUNNING);
/*
* NOTE: we don't remove ourselves from the waitqueue because
* we are the only user of it.
*/
/* queue_me and wait for wakeup, timeout, or a signal. */
futex_wait_queue_me(hb, &q, to, &wait);
/* If we were woken (and unqueued), we succeeded, whatever. */
ret = 0;
if (!unqueue_me(&q))
goto out_put_key;
ret = -ETIMEDOUT;
if (rem)
if (to && !to->task)
goto out_put_key;
/*
@ -1275,6 +1285,10 @@ retry_private:
out_put_key:
put_futex_key(fshared, &q.key);
out:
if (to) {
hrtimer_cancel(&to->timer);
destroy_hrtimer_on_stack(&to->timer);
}
return ret;
}