Messages in this thread | | | Date | Tue, 6 Apr 2010 19:42:35 +0800 | From | anfei <> | Subject | Re: [PATCH -mm 2/4] oom: select_bad_process: PF_EXITING check should take ->mm into account |
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On Fri, Apr 02, 2010 at 08:32:16PM +0200, Oleg Nesterov wrote: > select_bad_process() checks PF_EXITING to detect the task which > is going to release its memory, but the logic is very wrong. > > - a single process P with the dead group leader disables > select_bad_process() completely, it will always return > ERR_PTR() while P can live forever > > - if the PF_EXITING task has already released its ->mm > it doesn't make sense to expect it is goiing to free > more memory (except task_struct/etc) > > Change the code to ignore the PF_EXITING tasks without ->mm. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> > --- > > mm/oom_kill.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- MM/mm/oom_kill.c~2_FIX_PF_EXITING 2010-04-02 18:51:05.000000000 +0200 > +++ MM/mm/oom_kill.c 2010-04-02 18:58:37.000000000 +0200 > @@ -322,7 +322,7 @@ static struct task_struct *select_bad_pr > * the process of exiting and releasing its resources. > * Otherwise we could get an easy OOM deadlock. > */ > - if (p->flags & PF_EXITING) { > + if ((p->flags & PF_EXITING) && p->mm) {
Even this check is satisfied, it still can't say p is a good victim or it will release memory automatically if multi threaded, as the exiting of p doesn't mean the other threads are going to exit, so the ->mm won't be released.
> if (p != current) > return ERR_PTR(-1UL); > >
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