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 7FE7EC433FE for ; Wed, 16 Nov 2022 09:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233686AbiKPJs7 (ORCPT ); Wed, 16 Nov 2022 04:48:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233070AbiKPJs5 (ORCPT ); Wed, 16 Nov 2022 04:48:57 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D85B5F86 for ; Wed, 16 Nov 2022 01:48:56 -0800 (PST) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 38811336E7; Wed, 16 Nov 2022 09:48:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1668592135; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=lwhjYbNBUd3PtUYV/XWub7bHHJtVJkMKjMJnNEBApUI=; b=ezOrrIsACMJF3SEsu4t+uXp7G1RqSyq2yGm6afMXQCUfqtFimEI7nqhXkI2xe3TgjmOKon QcQVaCAMN9P21/gntGR6j++HRI/YCCtIdD18K0t0VQJrMxUfQbwPvEGCeHJu2UUug80vsE BJ6Ab/HTgbt7hx7wrateAGJ68zY2e8c= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id E87432C14F; Wed, 16 Nov 2022 09:48:54 +0000 (UTC) Date: Wed, 16 Nov 2022 10:48:54 +0100 From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: replay log: Re: [PATCH printk v4 38/39] printk: relieve console_lock of list synchronization duties Message-ID: References: <20221114162932.141883-1-john.ogness@linutronix.de> <20221114162932.141883-39-john.ogness@linutronix.de> <87tu30maqf.fsf@jogness.linutronix.de> <87y1sbjn77.fsf@jogness.linutronix.de> <87v8nfjn0d.fsf@jogness.linutronix.de> <87sfijjmgc.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87sfijjmgc.fsf@jogness.linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2022-11-16 10:14:35, John Ogness wrote: > Hi Petr, > > Sorry, console_flush_all() only loses the console_lock if there was a > handover. Here is a new complete suggestion from me. > > if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) { > /* Get a consistent copy of @syslog_seq. */ > mutex_lock(&syslog_lock); > newcon->seq = syslog_seq; > mutex_unlock(&syslog_lock); > } else { > /* Begin with next message added to ringbuffer. */ > newcon->seq = prb_next_seq(prb); > > /* > * If any enabled boot consoles are due to be unregistered > * shortly, some may not be caught up and may be the same > * device as @newcon. Since it is not known which boot console > * is the same device, flush all consoles and, if necessary, > * start with the message of the enabled boot console that is > * the furthest behind. > */ > if (bootcon_registered && !keep_bootcon) { > bool handover; > > /* > * Hold the console_lock to guarantee safe access to > * console->seq. > */ > console_lock(); > > /* > * Flush all consoles and set the console to start at > * the next unprinted sequence number. > */ > if (!console_flush_all(true, &newcon->seq, &handover)) { > /* > * Flushing failed. Just choose the lowest > * sequence of the enabled boot consoles. > */ > > /* > * If there was a handover, this context no > * longer holds the console_lock. > */ > if (handover) > console_lock(); > > newcon->seq = prb_next_seq(prb); > for_each_console(con) { > if ((con->flags & CON_BOOT) && > (con->flags & CON_ENABLED) && > con->seq < newcon->seq) { > newcon->seq = con->seq; > } > } > } > > console_unlock(); > } It looks good to me. Now, we just need to agree how to add this into the patchset. My proposal is to: 1. patch: hide the original code into a function, .e.g. console_init_seq() 2. patch: move console_init_seq() and add the above trickery Do both before the 3rd patch in this patchset. It moved the code outside console_lock() guarded section. Best Regards, Petr