Messages in this thread | | | Date | Thu, 21 Jan 2010 19:13:13 +0200 | From | Avi Kivity <> | Subject | Re: [PATCHv2 1/3] eventfd: allow atomic read and waitqueue remove |
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On 01/21/2010 06:58 PM, Davide Libenzi wrote: > On Thu, 21 Jan 2010, Michael S. Tsirkin wrote: > > >> This is a backport of commit: 03db343a6320f780937078433fa7d8da955e6fce >> modified in a way that introduces some code duplication on the one hand, >> but reduces the risk of regressing existing eventfd users on the other >> hand. >> >> KVM needs a wait to atomically remove themselves from the eventfd >> ->poll() wait queue head, in order to handle correctly their IRQfd >> deassign operation. >> >> This patch introduces such API, plus a way to read an eventfd from its >> context. >> >> Signed-off-by: Michael S. Tsirkin<mst@redhat.com> >> --- >> >> Avi, Davidel, how about only including the following part for -stable >> then? Reason is, I still would like to be able to use irqfd there, and >> getting spurious interrupts 100% of times unmask is done isn't a very >> good idea IMO ... >> > It's the same thing. Unless there are *real* problems in KVM due to the > spurious ints, I still think this is .33 material. >
I agree.
But I think we can solve this in another way in .32: we can clear the eventfd from irqfd->inject work, which is in process context. The new stuff is only needed for lockless clearing, no?
-- Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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