From: Corey Minyard <cminyard@xxxxxxxxxx> If you have a process with less than 1000 totalpages, the calculation: adj = (long)p->signal->oom_score_adj; ... adj *= totalpages / 1000; will always result in adj being zero no matter what oom_score_adj is, which could result in the wrong process being picked for killing. Fix by adding 1000 to totalpages before dividing. Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx> --- I ran across this trying to diagnose another problem where I set up a cgroup with a small amount of memory and couldn't get a test program to work right. I'm not sure this is quite right, to keep closer to the current behavior you could do: if (totalpages >= 1000) adj *= totalpages / 1000; but that would map 0-1999 to the same value. But this at least shows the issue. I can provide a test program the shows the issue, but I think it's pretty obvious from the code. mm/oom_kill.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index eefd3f5fde46..4ae0b6193bcd 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -233,8 +233,11 @@ long oom_badness(struct task_struct *p, unsigned long totalpages) mm_pgtables_bytes(p->mm) / PAGE_SIZE; task_unlock(p); - /* Normalize to oom_score_adj units */ - adj *= totalpages / 1000; + /* + * Normalize to oom_score_adj units. You should never + * multiply by zero here, or oom_score_adj will not work. + */ + adj *= (totalpages + 1000) / 1000; points += adj; return points; -- 2.25.1
