Re: [PATCH v2 1/2] kvm: x86: Fix racy event propagation in kmv timer

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On Tue, Jun 09, 2009 at 03:37:01PM +0200, Jan Kiszka wrote:
> v2 as requested in private discussion: Broken into two pieces, and the
> second one will not change the original semantic.
> 
> -------------->
> 
> Minor issue that likely had no practical relevance: The kvm timer
> function so far incremented the pending counter and then may reset it
> again to 1 in case reinjection was disabled. This opened a small racy
> window with the corresponding VCPU loop that may have happened to run on
> another (real) CPU and already consumed the value.
> 
> Fix it by skipping the incrementation in case pending is already > 0.
> This opens a different race windows, but may only rarely cause lost
> events in case we do not care about them anyway (!reinject).
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

ACK both, thanks.

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