Re: [PATCH] mm: sync rss-counters at the end of exit_mm()

[KOSAKI Motohiro]

On Mon, Apr 9, 2012 at 4:03 PM, Konstantin Khlebnikov
<khlebnikov@xxxxxxxxxx> wrote:
> On task's exit do_exit() calls sync_mm_rss() but this is not enough,
> there can be page-faults after this point, for example exit_mm() ->
> mm_release() -> put_user() (for processing tsk->clear_child_tid).
> Thus there may be some rss-counters delta in current->rss_stat.

Seems reasonable. but I have another question. Do we have any reason to
keep sync_mm_rss() in do_exit()? I havn't seen any reason that thread exiting
makes rss consistency.


>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> Reported-by: Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
>  kernel/exit.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/kernel/exit.c b/kernel/exit.c
> index d8bd3b42..8e09dbe 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -683,6 +683,7 @@ static void exit_mm(struct task_struct * tsk)
>        enter_lazy_tlb(mm, current);
>        task_unlock(tsk);
>        mm_update_next_owner(mm);
> +       sync_mm_rss(mm);
>        mmput(mm);
>  }
>
>
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