On 04/01, David Rientjes wrote:
>
> On Thu, 1 Apr 2010, Oleg Nesterov wrote:
>
> > > You can't do this for the reason I cited in another email, oom_badness()
> > > returning 0 does not exclude a task from being chosen by
> > > selcet_bad_process(), it will use that task if nothing else has been found
> > > yet. We must explicitly filter it from consideration by checking for
> > > !p->mm.
> >
> > Yes, you are right. OK, oom_badness() can never return points < 0,
> > we can make it int and oom_badness() can return -1 if !mm. IOW,
> >
> > - unsigned int points;
> > + int points;
> > ...
> >
> > points = oom_badness(...);
> > if (points >= 0 && (points > *ppoints || !chosen))
> > chosen = p;
> >
>
> oom_badness() and its predecessor badness() in mainline never return
> negative scores, so I don't see the value in doing this; just filter the
> task in select_bad_process() with !p->mm as it has always been done.
David, you continue to ignore my arguments ;) select_bad_process()
must not filter out the tasks with ->mm == NULL.
Once again:
void *memory_hog_thread(void *arg)
{
for (;;)
malloc(A_LOT);
}
int main(void)
{
pthread_create(memory_hog_thread, ...);
syscall(__NR_exit, 0);
}
Now, even if we fix PF_EXITING check, select_bad_process() will always
ignore this process. The group leader has ->mm == NULL.
See?
That is why I think we need something like find_lock_task_mm() in the
pseudo-patch I sent.
Or I missed something?
Oleg.
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