Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 7 Jun 2012 18:18:28 -0700 | Subject | Re: [patch 12/12] mm: correctly synchronize rss-counters at exit/exec |
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On Thu, Jun 7, 2012 at 6:05 PM, Markus Trippelsdorf <markus@trippelsdorf.de> wrote: > > You've somehow merged the wrong patch. > The correct version can be found here: > http://marc.info/?l=linux-kernel&m=133848759505805
It looks like Andrew sent me a bad version.
However, that patch you point at isn't good *either*.
It does totally insane things in xacct_add_tsk(). You can't call "sync_mm_rss(mm)" on somebody elses mm, yet that is exactly what it does (and you can't pass in another thread pointer either, since the whole point of the per-thread counters is that they don't have locking and aren't atomic, so you can't read them from any other context than "current").
The thing is, the *only* point where it makes sense to sync the rss pointers is when you detach the mm from the current thread. And possibly at "fork()" time, *before* you duplicate the "struct task_struct" and pollute the new one with stale rss counter values from the old one.
So doing sync_mm_rss() in xacct_add_tsk() is crazy. Doing it *anywhere* where mm is not clearly "current->mm" is wrong. If there is a "get_task_mm()" or similar nearby, it's wrong, it's crap, and it shouldn't be done.
Oleg, please rescue me? Your patch looks much closer to sane, but it's not quite there..
Linus
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