Messages in this thread | | | From | Gregory Haskins <> | Subject | Re: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifier interface | Date | Fri, 19 Jun 2009 14:51:21 -0400 |
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Davide Libenzi wrote: > On Thu, 18 Jun 2009, Gregory Haskins wrote: > >> >> But the fact is: I do not see any way to actually use your referenceless >> POLLHUP release code in a race free way without doing something like I >> propose in 3/4, 4/4. Lets keep the discussion focused on that for now, >> if we could. > > OK, since I got literally swamped by the amount of talks and patches over > this theoretically simple topic, would you mind 1) posting the global > patch over eventfd
Done. Should show up as replies to this email. These apply to v2.6.30 and are devoid of any KVM-isms. :)
(Note-1: I've built and run these patches against additional kvm/irqfd patches and verified they all work properly)
(Note-2: I included your POLLHUP patch as 1/3 since it currently only exists in kvm.git, and is a pre-req for the other two)
> 2) describe exactly what races are you talking about
Covered in the patch headers (3/3 probably has the most detail)
> 3) explain why this should be any concern of eventfd at all? >
To support any in-kernel eventfd client that wants to get both "signal" and "release" notifications (based on using your POLLHUP patch) in a race-free way. Without 2/3, 3/3, I cannot see how this can be done. Yet your 1/3 patch is an important enhancement (to at least one client). I suspect any other in-kernel users will find this a good feature as well.
Thanks Davide, -Greg
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