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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,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 A1FD1C43441 for ; Fri, 23 Nov 2018 02:40:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A13320820 for ; Fri, 23 Nov 2018 02:40:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vVV2ghZB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A13320820 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407971AbeKWNXJ (ORCPT ); Fri, 23 Nov 2018 08:23:09 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:43901 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728436AbeKWNXJ (ORCPT ); Fri, 23 Nov 2018 08:23:09 -0500 Received: by mail-pg1-f196.google.com with SMTP id v28so2406276pgk.10 for ; Thu, 22 Nov 2018 18:40:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=/Wy8CQ3X8SY/C9/CSYvkmwYCm8PZOvVaoL1d3mWNPC8=; b=vVV2ghZB6yYcq80oTFa48sKNgJYv/fPahoGUH83qAMnVROm3SUY1aMpZr79K+4iKaz 80njRIztvoL0D/KNVs4W7iIgu0I2aE13lpyoubX6+oihtr/27zbPib1Lb1Ty7OT0l0Er 1Iw8sVjpnXlF9lHVsg1YszM8yM8IhM5sssrFGXPeI+zxpqaz/h5xVThJHCmjB130BCOk ajm5LR1uY33Clx+GFtvgeLspAoo56N559Vi3jpKJUK1eWiJA5dWDUXp63RYjuy0lX9YQ 7ApNoUW5bwvc5ev2noXLcHFiTCwDtGAW/iHIrG5pbVd6h++IvN7Wm+3DyfnNIkmZ71eI PQUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=/Wy8CQ3X8SY/C9/CSYvkmwYCm8PZOvVaoL1d3mWNPC8=; b=RlrxL5gMRw2l88rpbOXsBZW8s/A6Y+cjHH64W4sOry53hTB/H8IzpEl7LuxWuFHhNl EAV6ueBWmLQDO3+bXKANkCxvzv/6rImGkr9lWJsOeqLkEzhbPwBbpZq7278/0hPtTaDw /rq0bH6vjl32LMbLzfeK0DBM1bg6HfLwCTaivQsqF37tw7k1LCuQpgaC251FkgBsmN6f qIGnmkZAH6bpf73irkYKX/n8IBHet0JMNN+172lL+B8YCVjlpzCKnWUHiaD7i63AFa30 6VhI4gVgaCuu5V3RSJul0kKOLRemexIHw3TfDJc2QBRvB3oQGLZ7QJhvI/MzmRecYaU4 2SbQ== X-Gm-Message-State: AA+aEWZ4QyhBKNu6eU6CG6E0G7e65oqIYsaDaAa0TjF8s3Xg1bFM2UDi fZ4T6cIcvnfg7UuwrFJTGYA= X-Google-Smtp-Source: AJdET5ctTEbSx3x8h0RTbUSd7jFBB9lZdxyTcwFbiNVOrOGTAm0baeJ0kfkH3qRi00BdKDxYv4t7Wg== X-Received: by 2002:a63:dd15:: with SMTP id t21mr11912750pgg.347.1542940852599; Thu, 22 Nov 2018 18:40:52 -0800 (PST) Received: from localhost ([175.223.19.111]) by smtp.gmail.com with ESMTPSA id 128-v6sm58545735pfd.64.2018.11.22.18.40.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 22 Nov 2018 18:40:51 -0800 (PST) Date: Fri, 23 Nov 2018 11:40:48 +0900 From: Sergey Senozhatsky To: Peter Zijlstra Cc: Sergey Senozhatsky , Waiman Long , Ingo Molnar , Will Deacon , Thomas Gleixner , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Tejun Heo , Andrew Morton , Steven Rostedt Subject: Re: [PATCH v2 07/17] debugobjects: Move printk out of db lock critical sections Message-ID: <20181123024048.GD1582@jagdpanzerIV> References: <1542653726-5655-1-git-send-email-longman@redhat.com> <1542653726-5655-8-git-send-email-longman@redhat.com> <2ddd9e3d-951e-1892-c941-54be80f7e6aa@redhat.com> <20181122020422.GA3441@jagdpanzerIV> <20181122101606.GP2131@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181122101606.GP2131@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (11/22/18 11:16), Peter Zijlstra wrote: > > So maybe we need to switch debug objects print-outs to _always_ > > printk_deferred(). Debug objects can be used in code which cannot > > do direct printk() - timekeeping is just one example. > > No, printk_deferred() is a disease, it needs to be eradicated, not > spread around. deadlock-free printk() is deferred, but OK. Another idea then: --- diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 70935ed91125..3928c2b2f77c 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -323,10 +323,13 @@ static void debug_print_object(struct debug_obj *obj, char *msg) void *hint = descr->debug_hint ? descr->debug_hint(obj->object) : NULL; limit++; + + bust_spinlocks(1); WARN(1, KERN_ERR "ODEBUG: %s %s (active state %u) " "object type: %s hint: %pS\n", msg, obj_states[obj->state], obj->astate, descr->name, hint); + bust_spinlocks(0); } debug_objects_warnings++; } --- This should make serial consoles re-entrant. So printk->console_driver_write() hopefully will not deadlock. IOW, this turns serial consoles into early_consoles, for a while ;) -ss