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SubjectRe: [RESEND PATCH] kernfs: Avoid re-adding kernfs_node into kernfs_notify_list.

On Wed, Jul 06, 2022 at 06:18:28AM +1000, Imran Khan wrote:
> In this case, the point of using llist would be to avoid taking the locks in
> consumer.

Given that the consumer can dispatch the whole list, I doubt that's worth
the complication.

> Hmm. My idea was that eventually we will never run into situation where multiple
> producers will end up adding the same node because as soon as first producer
> adds the node (the other potential adders are spinning on kernfs_notify_lock),
> kn-> will get a non-NULL value and checking
> (kn-> != NULL) will avoid the node getting re-added.

So, here, I don't see how llist can be used without a surrounding lock and I
don't see much point in using llist if we need to use a lock anyway. If this
needs to be made scalable, we need a different strategy (e.g. per-cpu lock /
pending list can be an option).

I'm a bit swamped with other stuff and will likely be less engaged from now
on. I'll try to review patches where possible.



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