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. This has been demostrated already where sysrq+f couldn't trigger OOM killer because the work item to do so was waiting for a worker which never came... So I think we probably need to do this in the OOM killer context (with try_lock) or hand over to a special kernel thread. I am not sure a special kernel thread is really worth that but maybe it will turn out to be a better choice. -- Michal Hocko SUSE Labs -- 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>