On 07/23, Linus Torvalds wrote:
>
> IOW, I think we should do something like this (this is on top of my
> patch, since it has that wake_page_function() change in it, but notice
> how we have the exact same issue in our traditional
> autoremove_wake_function() usage).
...
> +static inline void list_del_init_careful(struct list_head *entry)
> +{
> + __list_del_entry(entry);
> + entry->prev = entry;
> + smp_store_release(&entry->next, entry);
> +}
> +
...
> static inline int list_empty_careful(const struct list_head *head)
> {
> - struct list_head *next = head->next;
> + struct list_head *next = smp_load_acquire(&head->next);
> return (next == head) && (next == head->prev);
> }
This (and your previous email) answers my concerns about memory barriers.
IIUC, finish_wait() could even use this version of list_empty_careful(),
struct list_head *next = smp_load_acquire(&head->next);
return (next == head) && !WARN_ON(next != head->prev);
iow, it doesn't really need to check next == head->prev as long as only
list_del_init_careful() can remove it from list.
Thanks!
Oleg.
