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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 C6194C32789 for ; Sat, 3 Nov 2018 02:00:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 86B222082D for ; Sat, 3 Nov 2018 02:00:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86B222082D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp 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 S1728573AbeKCLJp (ORCPT ); Sat, 3 Nov 2018 07:09:45 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:48851 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbeKCLJp (ORCPT ); Sat, 3 Nov 2018 07:09:45 -0400 Received: from fsav403.sakura.ne.jp (fsav403.sakura.ne.jp [133.242.250.102]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id wA3208Fh083047; Sat, 3 Nov 2018 11:00:09 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav403.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav403.sakura.ne.jp); Sat, 03 Nov 2018 11:00:08 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav403.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157065137.bbtec.net [60.157.65.137]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id wA3208xQ083035 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 3 Nov 2018 11:00:08 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages. To: Peter Zijlstra Cc: Petr Mladek , Sergey Senozhatsky , Sergey Senozhatsky , Dmitriy Vyukov , Steven Rostedt , Alexander Potapenko , Fengguang Wu , Josh Poimboeuf , LKML , Linus Torvalds , Andrew Morton , linux-mm@kvack.org, Ingo Molnar , Will Deacon References: <1541165517-3557-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <1541165517-3557-3-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20181102133629.GN3178@hirez.programming.kicks-ass.net> From: Tetsuo Handa Message-ID: <80eb808d-4c17-9b1f-f866-3e22b9b2b18e@i-love.sakura.ne.jp> Date: Sat, 3 Nov 2018 11:00:10 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181102133629.GN3178@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/11/02 22:36, Peter Zijlstra wrote: > On Fri, Nov 02, 2018 at 10:31:57PM +0900, Tetsuo Handa wrote: >> syzbot is sometimes getting mixed output like below due to concurrent >> printk(). Mitigate such output by using line-buffered printk() API. >> >> RCU used illegally from idle CPU! >> rcu_scheduler_active = 2, debug_locks = 1 >> RSP: 0018:ffffffff88007bb8 EFLAGS: 00000286 >> RCU used illegally from extended quiescent state! >> ORIG_RAX: ffffffffffffff13 >> 1 lock held by swapper/1/0: >> RAX: dffffc0000000000 RBX: 1ffffffff1000f7b RCX: 0000000000000000 >> #0: >> RDX: 1ffffffff10237b8 RSI: 0000000000000001 RDI: ffffffff8811bdc0 >> 000000004b34587c >> RBP: ffffffff88007bb8 R08: ffffffff88075e00 R09: 0000000000000000 >> ( >> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 >> rcu_read_lock >> R13: ffffffff88007c78 R14: 0000000000000000 R15: 0000000000000000 >> ){....} >> arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline] >> default_idle+0xc2/0x410 arch/x86/kernel/process.c:498 >> , at: trace_call_bpf+0xf8/0x640 kernel/trace/bpf_trace.c:46 > > WTH is that buffered aPI, and no, that breaks my earlyprintk stuff. > This API is nothing but a wrapper for reducing frequency of directly calling printk() by using snprintf() if possible. Thus, whatever your earlyprintk stuff is, this API should not affect it.