From nobody Mon Apr 13 17:13:47 2026 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 893B4C433FE for ; Mon, 14 Nov 2022 16:30:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237611AbiKNQaQ (ORCPT ); Mon, 14 Nov 2022 11:30:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237528AbiKNQ3k (ORCPT ); Mon, 14 Nov 2022 11:29:40 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9189BEB1 for ; Mon, 14 Nov 2022 08:29:39 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1668443378; 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=6POxijvlWYTfJk68FJg54j07I7MpPRBTNu3UsEFQG6Y=; b=JCoPP84GTD7S6ZKvY3Z/oW1faIG0mRb+VXwmEMq2/9maJnu2bJ4vVZwAKdnWc0JkCEwziB u9Z4tPX23Yk6Dq1b8w2jERlxWFg9DZ6B8ebtpQpj8Eh/HGr1vYGrbZvZRaddeJKAO3LlQx J1TeVrqc45Q8oimpMKSBUzA7sN8i9CC+jZFqFP8+fC6nuurYGVkEgO8NfYHmsCdyslWqR3 r49w15/LRtFVLv5xvSxiCEuHQy5VVbMYf5zi6z8gKRt9MYYconzIJI69+2S8dLZ+WC4xuX LH/xD2yPO2uk1n/+PeJzAvnTu0vVvHmwItiLx5zxsIDDlP21zAWNhv2/dqOwtQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1668443378; 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=6POxijvlWYTfJk68FJg54j07I7MpPRBTNu3UsEFQG6Y=; b=XM0sZBUTpYOnV33YxdEq1ANzbOmI/ncNQRLlKWlmnypDTlRkCpe0fo3vqHy9OFToINmwjt D4N0MxF5n4UhX8DA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH printk v4 08/39] tty: tty_io: document console_lock usage Date: Mon, 14 Nov 2022 17:35:01 +0106 Message-Id: <20221114162932.141883-9-john.ogness@linutronix.de> In-Reply-To: <20221114162932.141883-1-john.ogness@linutronix.de> References: <20221114162932.141883-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" show_cons_active() uses the console_lock to gather information on registered consoles. Since the console_lock is being used for multiple reasons, explicitly document these reasons. This will be useful when the console_lock is split into fine-grained locking. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- drivers/tty/tty_io.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index de06c3c2ff70..ee4da2fec328 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3526,6 +3526,16 @@ static ssize_t show_cons_active(struct device *dev, struct console *c; ssize_t count =3D 0; =20 + /* + * Hold the console_lock to guarantee that no consoles are + * unregistered until all console processing is complete. + * This also allows safe traversal of the console list and + * race-free reading of @flags. + * + * Take console_lock to serialize device() callback with + * other console operations. For example, fg_console is + * modified under console_lock when switching vt. + */ console_lock(); for_each_console(c) { if (!c->device) --=20 2.30.2