Following the links, the full comment text is: /* On Xen the line below does not always work. Needs investigating! */ So this is in theory a lower priority

Following the links, the full comment text is: /* On Xen the line below does not always work. Needs investigating! */ So this is in theory a lower priority issue for the mainline kernel. Especially since it apparently hasn't caused problems for ~ 8-9 years during which Xen and Linux have been thoroughly put to the test (e.g. Amazon AWS). Could be a "tearing out your hair" desperate sort of thing where you cast around for any possible cause....