/**
* struct futex_q - The hashed futex queue entry, one per waiting task
+ * @list: priority-sorted list of tasks waiting on this futex
* @task: the task waiting on the futex
* @lock_ptr: the hash bucket lock
* @key: the key the futex is hashed on
*
* 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
+ * The order of wakeup is always to make the first condition true, then
* the second.
*
* PI futexes are typically woken before they are removed from the hash list via
* Slow path to fixup the fault we just took in the atomic write
* access to @uaddr.
*
- * We have no generic implementation of a non destructive write to the
+ * We have no generic implementation of a non-destructive write to the
* user address. We know that we faulted in the atomic pagefault
* disabled section so we can as well avoid the #PF overhead by
* calling get_user_pages() right away.
*/
pi_state = this->pi_state;
/*
- * Userspace might have messed up non PI and PI futexes
+ * Userspace might have messed up non-PI and PI futexes
*/
if (unlikely(!pi_state))
return -EINVAL;
/*
* We set q->lock_ptr = NULL _before_ we wake up the task. If
- * a non futex wake up happens on another CPU then the task
- * might exit and p would dereference a non existing task
+ * a non-futex wake up happens on another CPU then the task
+ * might exit and p would dereference a non-existing task
* struct. Prevent this by holding a reference on p across the
* wake up.
*/
/**
* futex_requeue() - Requeue waiters from uaddr1 to uaddr2
- * uaddr1: source futex user address
- * uaddr2: target futex user address
- * nr_wake: number of waiters to wake (must be 1 for requeue_pi)
- * nr_requeue: number of waiters to requeue (0-INT_MAX)
- * requeue_pi: if we are attempting to requeue from a non-pi futex to a
+ * @uaddr1: source futex user address
+ * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
+ * @uaddr2: target futex user address
+ * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
+ * @nr_requeue: number of waiters to requeue (0-INT_MAX)
+ * @cmpval: @uaddr1 expected value (or %NULL)
+ * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
* pi futex (pi to pi requeue is not supported)
*
* Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
/* The key must be already stored in q->key. */
static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
+ __acquires(&hb->lock)
{
struct futex_hash_bucket *hb;
- get_futex_key_refs(&q->key);
hb = hash_futex(&q->key);
q->lock_ptr = &hb->lock;
static inline void
queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
+ __releases(&hb->lock)
{
spin_unlock(&hb->lock);
- drop_futex_key_refs(&q->key);
}
/**
* an example).
*/
static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
+ __releases(&hb->lock)
{
int prio;
* and dropped here.
*/
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);
q->pi_state = NULL;
spin_unlock(q->lock_ptr);
-
- drop_futex_key_refs(&q->key);
}
/*
}
retry:
- /* Prepare to wait on uaddr. */
+ /*
+ * Prepare to wait on uaddr. On success, holds hb lock and increments
+ * q.key refs.
+ */
ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
if (ret)
goto out;
/* If we were woken (and unqueued), we succeeded, whatever. */
ret = 0;
+ /* unqueue_me() drops q.key ref */
if (!unqueue_me(&q))
- goto out_put_key;
+ goto out;
ret = -ETIMEDOUT;
if (to && !to->task)
- goto out_put_key;
+ goto out;
/*
* We expect signal_pending(current), but we might be the
* victim of a spurious wakeup as well.
*/
- if (!signal_pending(current)) {
- put_futex_key(fshared, &q.key);
+ if (!signal_pending(current))
goto retry;
- }
ret = -ERESTARTSYS;
if (!abs_time)
- goto out_put_key;
+ goto out;
restart = ¤t_thread_info()->restart_block;
restart->fn = futex_wait_restart;
- restart->futex.uaddr = (u32 *)uaddr;
+ restart->futex.uaddr = uaddr;
restart->futex.val = val;
restart->futex.time = abs_time->tv64;
restart->futex.bitset = bitset;
ret = -ERESTART_RESTARTBLOCK;
-out_put_key:
- put_futex_key(fshared, &q.key);
out:
if (to) {
hrtimer_cancel(&to->timer);
static long futex_wait_restart(struct restart_block *restart)
{
- u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
+ u32 __user *uaddr = restart->futex.uaddr;
int fshared = 0;
ktime_t t, *tp = NULL;
q.rt_waiter = &rt_waiter;
q.requeue_pi_key = &key2;
- /* Prepare to wait on uaddr. */
+ /*
+ * Prepare to wait on uaddr. On success, increments q.key (key1) ref
+ * count.
+ */
ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
if (ret)
goto out_key2;
* In order for us to be here, we know our q.key == key2, and since
* we took the hb->lock above, we also know that futex_requeue() has
* completed and we no longer have to concern ourselves with a wakeup
- * race with the atomic proxy lock acquition by the requeue code.
+ * race with the atomic proxy lock acquisition by the requeue code. The
+ * futex_requeue dropped our key1 reference and incremented our key2
+ * reference count.
*/
/* Check if the requeue code acquired the second futex for us. */
*/
static inline int fetch_robust_entry(struct robust_list __user **entry,
struct robust_list __user * __user *head,
- int *pi)
+ unsigned int *pi)
{
unsigned long uentry;
* of the complex code paths. Also we want to prevent
* registration of robust lists in that case. NULL is
* guaranteed to fault and we get -EFAULT on functional
- * implementation, the non functional ones will return
+ * implementation, the non-functional ones will return
* -ENOSYS.
*/
curval = cmpxchg_futex_value_locked(NULL, 0, 0);
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