Re: [Qemu-devel] Node deletion in aio_set_fd_handler

[Paolo Bonzini]

On 03/08/2018 04:42, Fam Zheng wrote:
> Paolo, is this else branch dead code (or bug?):
> 
>         /* If the lock is held, just mark the node as deleted */
>         if (qemu_lockcnt_count(&ctx->list_lock)) {
>             node->deleted = 1;
>             node->pfd.revents = 0;
>         } else {
>             /* Otherwise, delete it for real.  We can't just mark it as
>              * deleted because deleted nodes are only cleaned up while
>              * no one is walking the handlers list.
>              */
>             QLIST_REMOVE(node, node);
>             deleted = true;
>         }
> 
> Since we are in a qemu_lockcnt_lock/unlock section?

No, qemu_lockcnt_count returns the number of nested qemu_lockcnt_inc/dec
(read-side) sections.  lock/unlock is for the write side.

The comment should be improved (e.g. "if a read is in progress, just
mark the node as deleted").

Paolo