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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69B6CC433F5 for ; Wed, 16 Mar 2022 23:27:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345259AbiCPX2W (ORCPT ); Wed, 16 Mar 2022 19:28:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238816AbiCPX2U (ORCPT ); Wed, 16 Mar 2022 19:28:20 -0400 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B76D064C9 for ; Wed, 16 Mar 2022 16:27:04 -0700 (PDT) Received: by fieldses.org (Postfix, from userid 2815) id 178F148F; Wed, 16 Mar 2022 19:27:04 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 178F148F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1647473224; bh=oRYsFvRyGnJC9jPCSEJDJXYHIXXhCY6to725MbmUgcw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=c/dnTlCDgHcQLb45RiI7tGWzeG/aLYl7l5F6vMHl9LneBnVLLw5B1R9pluHIyW7Kl AYcTtNDv/fFDSyVu+OGXskiHqBGnzXo7gl83PbnzoSdvqP3Gmf+1Fjc6BI2a5EunGD qYGFderD8x4GKOeOQnqq1Jjs+gawz3GxkuaXPKR8= Date: Wed, 16 Mar 2022 19:27:04 -0400 From: "J. Bruce Fields" To: Peter Zijlstra Cc: Chengming Zhou , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: failure to boot after dc6e0818bc9a "sched/cpuacct: Optimize away RCU read lock" Message-ID: <20220316232704.GE16511@fieldses.org> References: <20220316174324.GA16511@fieldses.org> <20220316204806.GL8939@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220316204806.GL8939@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 16, 2022 at 09:48:06PM +0100, Peter Zijlstra wrote: > On Wed, Mar 16, 2022 at 01:43:24PM -0400, J. Bruce Fields wrote: > > One of my test VMs has been failing to boot linux-next recently. I > > finally got around to a bisect this morning, and it landed on the below. > > > > What other information would be useful to debug this? > > A more recent -next should have this commit in it: Ah, yep, it's booting again with today's -next. Thanks.--b. > > > commit f2aa197e4794bf4c2c0c9570684f86e6fa103e8b > Author: Chengming Zhou > Date: Sat Mar 5 11:41:03 2022 +0800 > > cgroup: Fix suspicious rcu_dereference_check() usage warning > > task_css_set_check() will use rcu_dereference_check() to check for > rcu_read_lock_held() on the read-side, which is not true after commit > dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock"). This > commit drop explicit rcu_read_lock(), change to RCU-sched read-side > critical section. So fix the RCU warning by adding check for > rcu_read_lock_sched_held(). > > Fixes: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock") > Reported-by: Linux Kernel Functional Testing > Reported-by: syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com > Signed-off-by: Chengming Zhou > Signed-off-by: Peter Zijlstra (Intel) > Acked-by: Tejun Heo > Tested-by: Zhouyi Zhou > Tested-by: Marek Szyprowski > Link: https://lore.kernel.org/r/20220305034103.57123-1-zhouchengming@bytedance.com > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 1e356c222756..0d1ada8968d7 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -450,6 +450,7 @@ extern struct mutex cgroup_mutex; > extern spinlock_t css_set_lock; > #define task_css_set_check(task, __c) \ > rcu_dereference_check((task)->cgroups, \ > + rcu_read_lock_sched_held() || \ > lockdep_is_held(&cgroup_mutex) || \ > lockdep_is_held(&css_set_lock) || \ > ((task)->flags & PF_EXITING) || (__c))