Kohli, Gaurav wrote: > On 3/9/2018 4:18 PM, Tetsuo Handa wrote: > > > Kohli, Gaurav wrote: > >>> t->alloc_lock is still held when leaving find_lock_task_mm(), which means > >>> that t->mm != NULL. But nothing prevents t from setting t->mm = NULL at > >>> exit_mm() from do_exit() and calling exit_creds() from __put_task_struct(t) > >>> after task_unlock(t) is called. Seems difficult to trigger race window. Maybe > >>> something has preempted because oom_badness() becomes outside of RCU grace > >>> period upon leaving find_lock_task_mm() when called from proc_oom_score(). > >> Hi Tetsuo, > >> > >> Yes it is not easy to reproduce seen twice till now and i agree with > >> your analysis. But David has already fixing this in different way, > >> So that also looks better to me: > >> > >> https://patchwork.kernel.org/patch/10265641/ > >> > > Yes, I'm aware of that patch. > > > >> But if need to keep that code, So we have to bump up the task > >> reference that's only i can think of now. > > I don't think so, for I think it is safe to call > > has_capability_noaudit(p) with p->alloc_lock held. > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index f2e7dfb..4efcfb8 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -222,7 +222,6 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > > */ > > points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + > > mm_pgtables_bytes(p->mm) / PAGE_SIZE; > > - task_unlock(p); > > > > /* > > * Root processes get 3% bonus, just like the __vm_enough_memory() > > @@ -230,6 +229,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > > */ > > if (has_capability_noaudit(p, CAP_SYS_ADMIN)) > > points -= (points * 3) / 100; > > + task_unlock(p); > > Earlier i have thought the same to post this, but this may create > problem if there are sleeping calls in > > has_capability_noaudit ? has_capability_noaudit() does not sleep. See what has_ns_capability_noaudit() is doing. > > > > > /* Normalize to oom_score_adj units */ > > adj *= totalpages / 1000; > > > -- > Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project. > > -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
