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    SubjectRe: [KVM PATCH v10] kvm: add support for irqfd
    On Thu, Jun 11, 2009 at 04:16:47PM +0300, Michael S. Tsirkin wrote:
    > > +
    > > + ret = file->f_op->poll(file, &irqfd->pt);
    > > + if (ret < 0)
    > > + goto fail;

    Looking at it some more, we have:
    struct file_operations {
    ....
    unsigned int (*poll) (struct file *, struct poll_table_struct *);

    So the comparison above does not seem to make sense:
    it seems that the return value from poll can not be negative.

    Will the callback be executed if someone did a write to eventfd
    before we attached it? If no, maybe we should call it here
    if ret != 0.


    > > +
    > > + irqfd->file = file;
    > > +
    > > + mutex_lock(&kvm->lock);
    > > + list_add_tail(&irqfd->list, &kvm->irqfds);
    > > + mutex_unlock(&kvm->lock);
    > > +
    > > + return 0;
    > > +
    > > +fail:
    > > + if (irqfd->wqh)
    > > + remove_wait_queue(irqfd->wqh, &irqfd->wait);
    >
    > Why are these 2 lines here? Either we might get a callback even though
    > poll failed - and then this test without lock is probably racy -
    > or we can't, and then we can replace the above with BUG_ON(irqfd->wqh).
    >
    > Which is it? I think the later ...
    >
    >
    > > +
    > > + if (file && !IS_ERR(file))
    > > + fput(file);
    > > +
    > > + kfree(irqfd);
    > > + return ret;
    > > +}
    > > +


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