On Sat, Jun 11, 2011 at 09:04:14AM -0700, Hugh Dickins wrote: > I had another go at reproducing it, 2 hours that time, then a try with > 692e0b35427a reverted: it ran overnight for 9 hours when I stopped it. > > Andrea, please would you ask Linus to revert that commit before -rc3? > Or is there something else you'd like us to try instead? I admit that > I've not actually taken the time to think through exactly how it goes > wrong, but it does look dangerous. Here I was asked if the mem_cgroup_newpage_charge need the mmap_sem at all. And if not why not to release the mmap_sem early. https://lkml.org/lkml/2011/3/14/276 So I didn't see why mmap_sem was needed, I also asked confirmation and who answered agreed it was safe without mmap_sem even if it's the only place doing that. Maybe that assumption was wrong and we need mmap_sem after all if this commit is causing problems. Or did you find something wrong in the actual patch? Do I understand right that the bug just that we must run alloc_hugepage_vma+mem_cgroup_newpage_charge within the same critical section protected by the mmap_sem read mode? Do we know why? > The way I reproduce it is with my tmpfs kbuilds swapping load, > in this case restricting mem by memcg, and (perhaps the important > detail, not certain) doing concurrent swapoff/swapon repeatedly - > swapoff takes another mm_users reference to the mm it's working on, > which can cause surprises. Ok. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>