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Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll |
Date: |
Fri, 21 Feb 2020 14:06:26 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 21/02/20 13:59, Stefan Hajnoczi wrote:
> 1. It doesn't crash if the node is currently not on a list.
> 2. It clears the node's linked list pointers so that future linked
> list operations (like QLIST_SAFE_REMOVE()) aren't accidentally
> performed on stale pointers.
>
> The node has a long lifespan and will be inserted into ready_lists
> multiple times. We need to safely remove it from ready_list to protect
> against a corruption the next time the node is inserted into a
> ready_list again:
Ah, so the one I singled out is for (2) (we know the node is currently
on a list), while the one below is for (1). Would it make sense to move
(2) to Q*_REMOVE_*? We can do it separately after this pull request.
> /* Add a handler to a ready list */
> static void add_ready_handler(AioHandlerList *ready_list,
> AioHandler *node,
> int revents)
> {
> QLIST_SAFE_REMOVE(node, node_ready); /* remove from nested parent's
> list */
> ^---- would cause corruption if node->node_ready was stale!
>
> Would you like me to add a comment?
No, it's okay.
Paolo
- [PATCH 1/5] aio-posix: fix use after leaving scope in aio_poll(), (continued)
- [PATCH 1/5] aio-posix: fix use after leaving scope in aio_poll(), Stefan Hajnoczi, 2020/02/14
- [PATCH 2/5] aio-posix: don't pass ns timeout to epoll_wait(), Stefan Hajnoczi, 2020/02/14
- [PATCH 3/5] qemu/queue.h: add QLIST_SAFE_REMOVE(), Stefan Hajnoczi, 2020/02/14
- [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Stefan Hajnoczi, 2020/02/14
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Sergio Lopez, 2020/02/19
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Paolo Bonzini, 2020/02/19
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Stefan Hajnoczi, 2020/02/21
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll,
Paolo Bonzini <=
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Stefan Hajnoczi, 2020/02/21
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Stefan Hajnoczi, 2020/02/21
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Paolo Bonzini, 2020/02/21
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Stefan Hajnoczi, 2020/02/21
- Re: [PATCH 5/5] aio-posix: make AioHandler dispatch O(1) with epoll, Paolo Bonzini, 2020/02/21
[PATCH 4/5] aio-posix: make AioHandler deletion O(1), Stefan Hajnoczi, 2020/02/14
Re: [PATCH 0/5] aio-posix: towards an O(1) event loop, Stefan Hajnoczi, 2020/02/21