[libvirt PATCH 1/2] nwfilter: update comment about locking filter updates

Ján Tomko jtomko at redhat.com
Thu Mar 10 10:25:48 UTC 2022

On a Thursday in 2022, Daniel P. Berrangé wrote:
>The comment against the 'updateMutex' refers to a problem with
>lock ordering when looking up filters in the virNWFilterObjList
>which uses an array. That problem does indeed exist.
>Unfortunately it claims that switching to a hash table would
>solve the lock ordering problems during instantiation. That
>is not correct because there is a second lock ordering
>problem related to how we traverse related filters when
>instantiating filters. Consider a set of filters:
>  Filter A:
>     Reference Filter C
>     Reference Filter D
>  Filter B:
>     Reference Filter D
>     Reference Filter C
>In one example, we lock A, C, D, in the other example
>we lock A, D, C.
>Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> src/nwfilter/nwfilter_gentech_driver.c | 57 ++++++++++++++++++++------
> 1 file changed, 45 insertions(+), 12 deletions(-)

Reviewed-by: Ján Tomko <jtomko at redhat.com>

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