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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E012EC2D0A8 for ; Mon, 28 Sep 2020 09:02:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B65E20E65 for ; Mon, 28 Sep 2020 09:02:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="nD81SSjn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726787AbgI1JCG (ORCPT ); Mon, 28 Sep 2020 05:02:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726328AbgI1JCC (ORCPT ); Mon, 28 Sep 2020 05:02:02 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16D50C0613CE for ; Mon, 28 Sep 2020 02:02:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=JC69PFZHwhcQINGVLis8MFtngUVCRlgWy9cisHR+b1o=; b=nD81SSjnDz+xKVR0dwrgT3OX9w ZI5R4ZFD0tqZhtT9a/IdKkYi4dh+NhHOw6T5RRUqbZDjmnr68TZI+mYnNd4r1RKTvWko2pQDMZFaT XJVbrtSFxdmqBEw1DeGtxZW+PsRIfk7WbCvzhZua2IsGXZswZmQemoz3Bji7UWnYGUM5U7zqYwQ+q 9VmwJ0ZZbX7UdcY0lZYGEIhFK9ICoBaqdV22VkGa3VXbEbVLRx4gR0iaSKhs7eABcLjoeP3ebMEwk BU5VeFLsC2VZMSAvo2rvbLr/irbxaJd5z/Ecq3sTa4YKdtgQLU74q8ZAlttQAzhqmNB8Ra+L44BvK ifsmSOEw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kMp2X-00006i-UD; Mon, 28 Sep 2020 09:01:46 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 743D8300F7A; Mon, 28 Sep 2020 11:01:43 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 5713F200D90B3; Mon, 28 Sep 2020 11:01:43 +0200 (CEST) Date: Mon, 28 Sep 2020 11:01:43 +0200 From: Peter Zijlstra To: Chengming Zhou Cc: linux-kernel@vger.kernel.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, songmuchun@bytedance.com Subject: Re: [External] Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule() Message-ID: <20200928090143.GA2628@hirez.programming.kicks-ass.net> References: <20200927161130.33172-1-zhouchengming@bytedance.com> <20200927161130.33172-2-zhouchengming@bytedance.com> <20200928073202.GA2611@hirez.programming.kicks-ass.net> <40ab934e-5b8b-735b-da65-3043efab9fdc@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <40ab934e-5b8b-735b-da65-3043efab9fdc@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 28, 2020 at 04:54:53PM +0800, Chengming Zhou wrote: > > 在 2020/9/28 下午3:32, Peter Zijlstra 写道: > > On Mon, Sep 28, 2020 at 12:11:30AM +0800, Chengming Zhou wrote: > >> The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be > >> deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause > >> deadlock on rq lock in the printk path. > > It also shouldn't happen in the first place, so who bloody cares. > > Yes, but if our box deadlock just because a WARN_ON_ONCE, we have to > reboot : ( You have to reboot anyway to get into the fixed kernel. > So these WARN_ON_ONCE have BUG_ON effect ?  Or we should change to use > BUG_ON ? Or use a sane printk implementation, I never suffer this.