On Tue, Aug 1, 2017 at 7:02 AM, Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote: > /* > * The full memory barrier implied by mm_cpumask update operations > * is required by the membarrier system call. > */ > > What we want to order here is: > > prev userspace memory accesses > schedule > <full mb> (it's already there) [A] > update to rq->curr changing the rq->curr->mm value > <full mb> (provided by mm_cpumask updates in switch_mm on x86) [B]
If I understand this right, the issue with relying on CR3 writes is that the target CPU could switch to a kernel thread and back to the same user mm white the membarrier caller is reading its mm, right?
