On 09/21, Michal Hocko wrote: > > On Mon 21-09-15 15:44:14, Oleg Nesterov wrote: > [...] > > So yes, in general oom_kill_process() can't call oom_unmap_func() directly. > > That is why the patch uses queue_work(oom_unmap_func). The workqueue thread > > takes mmap_sem and frees the memory allocated by user space. > > OK, this might have been a bit confusing. I didn't mean you cannot use > mmap_sem directly from the workqueue context. You _can_ AFAICS. But I've > mentioned that you _shouldn't_ use workqueue context in the first place > because all the workers might be blocked on locks and new workers cannot > be created due to memory pressure. Yes, yes, and I already tried to comment this part. We probably need a dedicated kernel thread, but I still think (although I am not sure) that initial change can use workueue. In the likely case system_unbound_wq pool should have an idle thread, if not - OK, this change won't help in this case. This is minor. > So I think we probably need to do this in the OOM killer context (with > try_lock) Yes we should try to do this in the OOM killer context, and in this case (of course) we need trylock. Let me quote my previous email: And we want to avoid using workqueues when the caller can do this directly. And in this case we certainly need trylock. But this needs some refactoring: we do not want to do this under oom_lock, otoh it makes sense to do this from mark_oom_victim() if current && killed, and a lot more details. and probably this is another reason why do we need MMF_MEMDIE. But again, I think the initial change should be simple. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>