> The IPMI driver uses read/write locks to ensure that things
> exist while they are in use. This is bad from a number of
> points of view. This patch removes the rwlocks and uses
> refcounts and a special synced list (the entries can be
> refcounted and removal is blocked while an entry is in
> use).
>
This:
> +
> +struct synced_list_entry_task_q
> {
> struct list_head link;
> + task_t *process;
> +};
> +
> +#define synced_list_for_each_entry(pos, l, entry, flags) \
> + for ((spin_lock_irqsave(&(l)->lock, flags), \
> + pos = container_of((l)->head.next, typeof(*(pos)),entry.link)); \
> + (prefetch((pos)->entry.link.next), \
> + &(pos)->entry.link != (&(l)->head) \
> + ? (atomic_inc(&(pos)->entry.usecount), \
> + spin_unlock_irqrestore(&(l)->lock, flags), 1) \
> + : (spin_unlock_irqrestore(&(l)->lock, flags), 0)); \
> + (spin_lock_irqsave(&(l)->lock, flags), \
> + synced_list_wake(&(pos)->entry), \
> + pos = container_of((pos)->entry.link.next, typeof(*(pos)), \
> + entry.link)))
(gad)
And this:
> +static int synced_list_clear(struct synced_list *head,
> + int (*match)(struct synced_list_entry *,
> + void *),
> + void (*free)(struct synced_list_entry *),
> + void *match_data)
> +{
> + struct synced_list_entry *ent, *ent2;
> + int rv = -ENODEV;
> + int mrv = SYNCED_LIST_MATCH_CONTINUE;
> +
> + spin_lock_irq(&head->lock);
> + restart:
> + list_for_each_entry_safe(ent, ent2, &head->head, link) {
> + if (match) {
> + mrv = match(ent, match_data);
> + if (mrv == SYNCED_LIST_NO_MATCH)
> + continue;
> + }
> + if (atomic_read(&ent->usecount)) {
> + struct synced_list_entry_task_q e;
> + e.process = current;
> + list_add(&e.link, &ent->task_list);
> + __set_current_state(TASK_UNINTERRUPTIBLE);
> + spin_unlock_irq(&head->lock);
> + schedule();
> + spin_lock_irq(&head->lock);
> + list_del(&e.link);
> + goto restart;
> + }
> + list_del(&ent->link);
> + rv = 0;
> + if (free)
> + free(ent);
> + if (mrv == SYNCED_LIST_MATCH_STOP)
> + break;
> + }
> + spin_unlock_irq(&head->lock);
> + return rv;
> +}
Look awfully similar to wait_queue_head_t. Are you sure existing
infrastructure cannot be used?
> 1 files changed, 692 insertions(+), 461 deletions(-)
Ow. Why is it worthwhile?
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