Davide Libenzi wrote:
> On Tue, 15 May 2007, Gregory Haskins wrote:
>
>
>>>>> On Tue, May 15, 2007 at 3:45 AM, in message <[EMAIL PROTECTED]>,
>>>>>
>> Avi Kivity <[EMAIL PROTECTED]> wrote:
>>
>>> Gregory Haskins wrote:
>>>
>>>> Signed- off- by: Gregory Haskins <[EMAIL PROTECTED]>
>>>> ---
>>>>
>>>> drivers/kvm/kvm.h | 1 +
>>>> drivers/kvm/kvm_main.c | 52
>>>> ++++++++++++++++++++++++++++++++++++++++++------
>>>> include/linux/kvm.h | 1 +
>>>> 3 files changed, 48 insertions(+), 6 deletions(- )
>>>>
>>>> diff -- git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
>>>> index 7b5d5e6..f5731c4 100644
>>>> --- a/drivers/kvm/kvm.h
>>>> +++ b/drivers/kvm/kvm.h
>>>> @@ - 333,6 +333,7 @@ struct kvm_vcpu_irq {
>>>> int deferred;
>>>> struct task_struct *task;
>>>> int guest_mode;
>>>> + int eventfd;
>>>>
>>>>
>>> Best to convert the fd to a filp when you install it. This avoids the
>>> conversion during runtime and allows you to do error checking earlier.
>>>
>> That was my initial impression also, but then I realized there was a
>> problem with that: Eventfd doesnt appear to have any way to notify
>> other entities when the fd is closed. Therefore the filp could be left
>> dangling in this case. By using the fd instead, I can validate the
>> pointer each time I need it. Perhaps Davide will have a suggestion
>> here.
>>
>
> I don't know how critical is the path where you will be doing check. The
> eventfd_fget() is pretty fast, so if you're not looking at a performance
> critical path, I'd suggest that. Otherwise you can do an early
> eventfd_get, and keep the file*. If you have no the ways to know if the
> userspace disconnected, an atomic_read(&file->f_count)==1 will tell you
> that you're the only owner of the file* (that is, userspace closed the
> eventfd descriptor). I'd give preference to the former option though.
>
We aren't really interested whether userspace is looking or not. After
all, it installed the eventfd, so it must be interested in the events.
> Avi, as you may have read from lkml, Andrew prefers the eventfd symbols
> export to come through the kvm tree, since they do not want to export
> symbols that so far has no module users.
>
>
Yes, I'll pick up the patch from lkml.
--
error compiling committee.c: too many arguments to function
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