On Fri, 19 Oct 2012, Glauber Costa wrote: > >>> Do we actually need to test PF_KTHREAD when current->mm == NULL? > >>> Perhaps because of aio threads whcih temporarily adopt a userspace mm? > >> > >> I believe so. I remember I discussed this in the past with David > >> Rientjes and he advised me to test for both. > >> > > > > PF_KTHREAD can do use_mm() to assume an ->mm but hopefully they aren't > > allocating slab while doing so. Have you considered actually charging > > current->mm->owner for that memory, though, since the kthread will have > > freed the memory before unuse_mm() or otherwise have charged it on behalf > > of a user process, i.e. only exempting PF_KTHREAD? > > > I always charge current->mm->owner. > Yeah, I'm asking have you considered charging current->mm->owner for the memory when a kthread (current) assumes the mm of a user process via use_mm()? It may free the memory before calling unuse_mm(), but it's also allocating the memory on behalf of a user so this exemption might be dangerous if use_mm() becomes more popular. I don't think there's anything that prevents that charge, I'm just wondering if you considered doing it even for kthreads with an mm. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>