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

April 09th, 2012 - 04:10 pm ET by Konstantin Khlebnikov | Report spam
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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.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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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#1 KOSAKI Motohiro
April 09th, 2012 - 05:10 pm ET | Report spam
On Mon, Apr 9, 2012 at 4:03 PM, Konstantin Khlebnikov
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
Reported-by: Markus Trippelsdorf
Cc: Hugh Dickins
Cc: KAMEZAWA Hiroyuki

 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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