From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2BBBC04AB3 for ; Mon, 27 May 2019 15:12:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 928A4217F4 for ; Mon, 27 May 2019 15:12:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726547AbfE0PMG (ORCPT ); Mon, 27 May 2019 11:12:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60032 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725991AbfE0PMG (ORCPT ); Mon, 27 May 2019 11:12:06 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ECD117FDFA; Mon, 27 May 2019 15:12:05 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.159]) by smtp.corp.redhat.com (Postfix) with SMTP id 2D197608A4; Mon, 27 May 2019 15:12:03 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 27 May 2019 17:12:05 +0200 (CEST) Date: Mon, 27 May 2019 17:12:02 +0200 From: Oleg Nesterov To: Minchan Kim Cc: Andrew Morton , LKML , linux-mm , Michal Hocko , Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon Subject: Re: [RFC 5/7] mm: introduce external memory hinting API Message-ID: <20190527151201.GB8961@redhat.com> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-6-minchan@kernel.org> <20190521153113.GA2235@redhat.com> <20190527074300.GA6879@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190527074300.GA6879@google.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 27 May 2019 15:12:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/27, Minchan Kim wrote: > > > another problem is that pid_task(pid) can return a zombie leader, in this case > > mm_access() will fail while it shouldn't. > > I'm sorry. I didn't notice that. However, I couldn't understand your point. > Why do you think mm_access shouldn't fail even though pid_task returns > a zombie leader? The leader can exit (call sys_exit(), not sys_exit_group()), this won't affect other threads. In this case the process is still alive even if the leader thread is zombie. That is why we have find_lock_task_mm(). Oleg.