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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT 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 63DEDC282DA for ; Wed, 17 Apr 2019 12:25:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C2192173C for ; Wed, 17 Apr 2019 12:25:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732141AbfDQMZB (ORCPT ); Wed, 17 Apr 2019 08:25:01 -0400 Received: from mx2.suse.de ([195.135.220.15]:49170 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729522AbfDQMZB (ORCPT ); Wed, 17 Apr 2019 08:25:01 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4EE4DAF8D; Wed, 17 Apr 2019 12:25:00 +0000 (UTC) Date: Wed, 17 Apr 2019 14:24:58 +0200 From: Petr Mladek To: Sergey Senozhatsky Cc: Feng Tang , Andrew Morton , Steven Rostedt , linux-kernel@vger.kernel.org, Kees Cook , Borislav Petkov , ying.huang@intel.com Subject: Re: [PATCH v2] panic: add an option to replay all the printk message in buffer Message-ID: <20190417122458.mhl3orevzha7sp6h@pathway.suse.cz> References: <20190410153718.22905-1-feng.tang@intel.com> <20190416211922.d3c9c6987f0b992da343be52@linux-foundation.org> <20190417064844.ppyqxcx2mgek5455@shbuild888> <20190417091832.z252cvcf4ktxeamv@pathway.suse.cz> <20190417094614.GB4260@jagdpanzerIV> <20190417105010.GA8492@jagdpanzerIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417105010.GA8492@jagdpanzerIV> User-Agent: NeoMutt/20170912 (1.9.0) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2019-04-17 19:50:10, Sergey Senozhatsky wrote: > On (04/17/19 18:46), Sergey Senozhatsky wrote: > > > > Does not look too complex/ugly. > > Looks simpler than adding one more global state to the > console_unlock() printing loop. > > // Not tested at all // > > diff --git a/kernel/panic.c b/kernel/panic.c > index cd73af35ec66..50eacfc9bc7e 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); > #define PANIC_PRINT_TIMER_INFO 0x00000004 > #define PANIC_PRINT_LOCK_INFO 0x00000008 > #define PANIC_PRINT_FTRACE_INFO 0x00000010 > +#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 > unsigned long panic_print; > > ATOMIC_NOTIFIER_HEAD(panic_notifier_list); > @@ -148,6 +149,9 @@ static void panic_print_sys_info(void) > > if (panic_print & PANIC_PRINT_FTRACE_INFO) > ftrace_dump(DUMP_ALL); > + > + if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) > + console_flush_on_panic(CONSOLE_FLUSH_ALL); The console must be replayed as the first thing in panic_print_sys_info(). Otherwise, the original messages are replaced by the other dumps. Especially ftrace_dump() might be pretty long. Also the names of the function and the parameter are misleading. All messages are already flushed when this is called. > } > > /** > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index 17102fd4c136..da60a185dbbb 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -2549,6 +2549,14 @@ void console_flush_on_panic(void) > */ > console_trylock(); > console_may_schedule = 0; > + if (flush_mode == CONSOLE_FLUSH_ALL) { > + /* > + * Can be done under logbuf lock, but it's unlikely that > + * we will have any race conditions here. > + */ > + console_seq = log_first_seq; > + console_idx = log_first_idx; I agree that it is easier. The cost is that the same messages are printed again without any explanation. I still think that it would be convenient to write a header line. It would help to understand the log for any, even 3rd-party, reader. Also it would help to find the beginning in a very long log. If the complexity of console_unlock() is the concern, we could refactor the code, e.g. put this "reset log" code into a separate function. Best Regards, Petr