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_PASS,USER_AGENT_MUTT autolearn=unavailable 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 249E0C43381 for ; Wed, 20 Mar 2019 15:01:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2D632184E for ; Wed, 20 Mar 2019 15:01:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727495AbfCTPA7 (ORCPT ); Wed, 20 Mar 2019 11:00:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53364 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726487AbfCTPA7 (ORCPT ); Wed, 20 Mar 2019 11:00:59 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5B8322D7E4; Wed, 20 Mar 2019 15:00:58 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.34]) by smtp.corp.redhat.com (Postfix) with SMTP id A218160BE2; Wed, 20 Mar 2019 15:00:55 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 20 Mar 2019 16:00:57 +0100 (CET) Date: Wed, 20 Mar 2019 16:00:54 +0100 From: Oleg Nesterov To: Michal Hocko Cc: syzbot , chanho.min@lge.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, pavel@ucw.cz, rafael.j.wysocki@intel.com, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: WARNING: syz-executor still has locks held! Message-ID: <20190320150053.GD21673@redhat.com> References: <0000000000000e4a41057b6c9792@google.com> <0000000000004cdec6058485b2ce@google.com> <20190320131655.GA8696@dhcp22.suse.cz> <20190320132410.GB21673@redhat.com> <20190320132936.GB8696@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320132936.GB8696@dhcp22.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 20 Mar 2019 15:00:59 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 03/20, Michal Hocko wrote: > > On Wed 20-03-19 14:24:11, Oleg Nesterov wrote: > > On 03/20, Michal Hocko wrote: > > > > > > Yes we do hold the cgred mutex while calling freezable_schedule but why > > > are we getting a warning is not really clear to me. The task should be > > > hidden from the freezer so why do we warn at all? > > > > try_to_freeze() calls debug_check_no_locks_held() and this makes sense. > > Yes it does. But it already ignores PF_NOFREEZE tasks and I fail to see > why is PF_FREEZER_SKIP any different. But they differ. PF_NOFREEZE is a "sticky" flag for kthreads. Set by default, cleared by set_freezable() if you want a freezable kthread. PF_FREEZER_SKIP means that a sleeping freezable task will call try_to_freeze() right after schedule() returns, so try_to_freeze_tasks() can safely count it as "already frozen". > it seems that skipping the task was the only viable option > to fix suspend issues Yes, de_thread() should use freezable_schedule(), iow I hope we will reconsider this (reverted) patch. > as removing the cgred is way way too complicated. We need to do this anyway, this leads to other more serious problems... Oleg.