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kernel/notifier.c: double register detection
By design notifiers can be registerd once only, 2nd register attempt called by mistake silently corrupts notifiers list. A few years ago I investigated described problem, the host was power cycled because of notifier list corruption. I've prepared this patch and applied it to the OpenVZ kernel and sent this patch but nobody commented on it. Later it helped us to detect a similar problem in the OpenVz kernel. Mistakes with notifier registration can happen for example during subsystem initialization from different namespaces, or because of a lost unregister in the roll-back path on initialization failures. The proposed check cannot prevent the described problem, however it allows us to detect its reason quickly without coredump analysis. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Vasily Averin <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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