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 AE13DC433FE for ; Mon, 7 Nov 2022 14:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232159AbiKGORR (ORCPT ); Mon, 7 Nov 2022 09:17:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232095AbiKGOQq (ORCPT ); Mon, 7 Nov 2022 09:16:46 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17CC71CFF6 for ; Mon, 7 Nov 2022 06:16:45 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1667830602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4n04ln6Ch/hdvzpbKZeVJtV0DW7GpBDW/64Z1krMb78=; b=fjFDBOuExj6AkzrBAgwGsZMWcQG7o8pcYxBeiRO9Hv5/MET+Urn/iU0k73K8KQVlMlUNpM FY+dleU7ocJj0ji81DsotW8vyOMG0D5M1iG7cmDJAaecNz7sH9SRPGHJJCmZcQBb+npM5o lJ0doKia/xvyGmtxJ5kwiPyMJtZqOe0h2Z2CxI35d7hqo2qKdthMC3yWtHOGMY88eLckEs 1Tz8RmJZ/H8/5654j9UFU19pDfIJWfawwbZHcQB+sptO2JpX6Oamb+OWlXEAFBWqGuOX3P n7AnRlDjpaJEB/ZcSIAtzUA/p3z/pTCXdt5NGwFbE/98sWE93QhtL7XkWfWFEQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1667830602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4n04ln6Ch/hdvzpbKZeVJtV0DW7GpBDW/64Z1krMb78=; b=i2mJNvHheKNDa4WvDo4khjz/Y4qbCG/JXNJubnpudAH/q8vUufrKnKB9RlhTArcA9d3SNr EtHCyjWatvPZE0AQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v3 05/40] printk: fix setting first seq for consoles Date: Mon, 7 Nov 2022 15:22:03 +0106 Message-Id: <20221107141638.3790965-6-john.ogness@linutronix.de> In-Reply-To: <20221107141638.3790965-1-john.ogness@linutronix.de> References: <20221107141638.3790965-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It used to be that all consoles were synchronized with respect to which message they were printing. After commit a699449bb13b ("printk: refactor and rework printing logic"), all consoles have their own @seq for tracking which message they are on. That commit also changed how the initial sequence number was chosen. Instead of choosing the next non-printed message, it chose the sequence number of the next message that will be added to the ringbuffer. That change created a possibility that a non-boot console taking over for a boot console might skip messages if the boot console was behind and did not have a chance to catch up before being unregistered. Since it is not possible to know which boot console a console is taking over, use the lowest @seq of all the enabled boot consoles. If no boot consoles are available/enabled, begin with the next message that will be added to the ringbuffer. Also, since boot consoles are meant to be used at boot time, handle them the same as CON_PRINTBUFFER to ensure that no initial messages are skipped. Signed-off-by: John Ogness --- kernel/printk/printk.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 173f46a29252..8974523f3107 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3222,14 +3222,26 @@ void register_console(struct console *newcon) } newcon->dropped = 0; - if (newcon->flags & CON_PRINTBUFFER) { + 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. */ + /* Begin with next message added to ringbuffer. */ newcon->seq = prb_next_seq(prb); + + /* + * If an enabled boot console is not caught up, start with + * that message instead. That boot console will be + * unregistered shortly and may be the same device. + */ + for_each_console(con) { + if ((con->flags & (CON_BOOT | CON_ENABLED)) == (CON_BOOT | CON_ENABLED) && + con->seq < newcon->seq) { + newcon->seq = con->seq; + } + } } /* -- 2.30.2