I hope it's not that frequent for production sites running RAC on
linux. ( We run on hpux ).

But I have heard a lot of people having problems in that area. ( That
does include remarks from people noting that prod linux systems have
experienced those symptoms at least on occassion or under load ).

When you start bundling the oracle clusterware with other things like
the oracle file system layer, etc ... it can get messy pretty quickly.

If you are contemplating a production system using linux it's
definitely something that needs to be addressed, understood, and
hopefully completely resolved.