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); /* Normalize to oom_score_adj units */ adj *= totalpages / 1000; -- 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
