Messages in this thread | | | Subject | Re: [ 11/48] mm: correctly synchronize rss-counters at exit/exec | From | Ben Hutchings <> | Date | Mon, 02 Jul 2012 03:01:59 +0100 |
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On Sun, 2012-07-01 at 12:02 -0700, Hugh Dickins wrote: > On Sun, 1 Jul 2012, Ben Hutchings wrote: > > > 3.2-stable review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Konstantin Khlebnikov <khlebnikov@openvz.org> > > > > commit 4fe7efdbdfb1c7e7a7f31decfd831c0f31d37091 upstream. > > > > do_exit() and exec_mmap() call sync_mm_rss() before mm_release() does > > put_user(clear_child_tid) which can update task->rss_stat and thus make > > mm->rss_stat inconsistent. This triggers the "BUG:" printk in check_mm(). > > > > Let's fix this bug in the safest way, and optimize/cleanup this later. > > > > Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> > > Cc: Oleg Nesterov <oleg@redhat.com> > > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > Cc: Hugh Dickins <hughd@google.com> > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> > > [bwh: Backported to 3.2: sync_mm_rss() still takes a struct task_struct *] > > Signed-off-by: Ben Hutchings <ben@decadent.org.uk> > > If you or Konstantin or Oleg have done full diligence on this, > to ensure that it is really applicable to 3.2 (not just that > the patch applies without rejects), fair enough.
I can't claim that, no.
> But I'd be cautious about it: it went through enough alternatives > and revisions that I wouldn't call it trivial; it's easy for me to > imagine that some of the affected paths were actually slightly different > in 3.2 days than they were in 3.4 days; and the disturbing warning that > these mods silence ("BUG: Bad rss-counter state ") did not exist before > 3.4 - unless you've ported that too?
No.
> That's not to assert that we had no rss problem at all before 3.4, > but we've not heard of any trouble from it. Caution tells me that > this patch might cause more trouble than it's worth.
Then I'll assume this should be dropped unless Konstantin or Oleg speaks up for it.
Ben.
-- Ben Hutchings When in doubt, use brute force. - Ken Thompson [unhandled content-type:application/pgp-signature] | |