On Wed, Dec 11, 2013 at 08:06:37PM -0500, Paul Gortmaker wrote:
> +/*
> + * Event API
> + */
> +#define __swait_event(wq, condition) \
> +do { \
> + DEFINE_SWAITER(__wait); \
> + \
> + for (;;) { \
> + swait_prepare(&wq, &__wait, TASK_UNINTERRUPTIBLE); \
> + if (condition) \
> + break; \
> + schedule(); \
> + } \
> + swait_finish(&wq, &__wait); \
> +} while (0)
> +
> +#define __swait_event_interruptible(wq, condition, ret)
> \
> +do { \
> + DEFINE_SWAITER(__wait); \
> + \
> + for (;;) { \
> + swait_prepare(&wq, &__wait, TASK_INTERRUPTIBLE); \
> + if (condition) \
> + break; \
> + if (signal_pending(current)) { \
> + ret = -ERESTARTSYS; \
> + break; \
> + } \
> + schedule(); \
> + } \
> + swait_finish(&wq, &__wait); \
> +} while (0)
> +
> +#define __swait_event_interruptible_timeout(wq, condition, ret)
> \
> +do { \
> + DEFINE_SWAITER(__wait); \
> + \
> + for (;;) { \
> + swait_prepare(&wq, &__wait, TASK_INTERRUPTIBLE); \
> + if (condition) \
> + break; \
> + if (signal_pending(current)) { \
> + ret = -ERESTARTSYS; \
> + break; \
> + } \
> + ret = schedule_timeout(ret); \
> + if (!ret) \
> + break; \
> + } \
> + swait_finish(&wq, &__wait); \
> +} while (0)
Urgh, please have a look at ___wait_event() we just killed all the
pointless replication for the normal waitqueues, please don't add more
of it.
> +unsigned int
> +__swake_up_locked(struct swait_queue_head *head, unsigned int state,
> + unsigned int num)
> +{
> + struct swaiter *curr, *next;
> + int woken = 0;
> +
> + list_for_each_entry_safe(curr, next, &head->task_list, node) {
> + if (wake_up_state(curr->task, state)) {
> + __swait_dequeue(curr);
> + /*
> + * The waiting task can free the waiter as
> + * soon as curr->task = NULL is written,
> + * without taking any locks. A memory barrier
> + * is required here to prevent the following
> + * store to curr->task from getting ahead of
> + * the dequeue operation.
> + */
> + smp_wmb();
> + curr->task = NULL;
> + if (++woken == num)
> + break;
> + }
> + }
> + return woken;
> +}
> +
> +unsigned int
> +__swake_up(struct swait_queue_head *head, unsigned int state, unsigned int
> num)
> +{
> + unsigned long flags;
> + int woken;
> +
> + if (!swaitqueue_active(head))
> + return 0;
> +
> + raw_spin_lock_irqsave(&head->lock, flags);
> + woken = __swake_up_locked(head, state, num);
> + raw_spin_unlock_irqrestore(&head->lock, flags);
> + return woken;
> +}
> +EXPORT_SYMBOL(__swake_up);
Urgh, fail. Do not put unbounded loops in raw_spin_lock.
I think I posted a patch a while back to cure this.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
