On Sat, Jun 11, 2011 at 07:51:36PM +0200, Johannes Weiner wrote: > This is a problem with the patch, but I think Kame's analysis and > approach to fix it are still correct. I agree with Kame's analysis too. This explains why removing the mmap_sem read mode introduced the problem, it was quite some unexpected subtleness not apparent to the naked eye, as memcg didn't explicitly relay on mmap_sem but it did implicitly during exit because of the __khugepaged_exit waiting if we were collapsing an hugepage... So the fix is safe because the task struct is freed with delayed_put_task_struct and that won't run until we rcu_read_unlock after mem_cgroup_from_task. Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Thanks, Andrea -- 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>