2011/6/12 Andrea Arcangeli <aarcange@xxxxxxxxxx>: > 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> > Thank you all. Regards, -Kame -- 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>