Messages in this thread | | | Date | Sat, 11 Jun 2011 20:44:16 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] [BUGFIX] update mm->owner even if no next owner. |
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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@redhat.com>
Thanks, Andrea
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