From nobody Mon Apr 13 17:09:52 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 50D60C4321E for ; Mon, 14 Nov 2022 16:30:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237568AbiKNQay (ORCPT ); Mon, 14 Nov 2022 11:30:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237607AbiKNQaP (ORCPT ); Mon, 14 Nov 2022 11:30:15 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2092922BC4 for ; Mon, 14 Nov 2022 08:29:44 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1668443382; 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=wX56Rx4ehD7yCLYC+HBYrPWlmwQCTi9+gNx/cMRdAa0=; b=sZwXHYkHvPbktNSwjxUK5aj2mlUfsNem40DSF6jkIhmjnLqme07Bj37zy8BIOHUrp4R+kO z20l7qtc9/VbGba0euziTCjOck6y0KeieHFYZ16r4/5p3EUfZkyVMuYj/ZUI1Y9PQXqyKQ wwabfaBCwER2N2R8NdsQJIhHmtea3R6RtskJewsP9Sc3cDiAnrz/ibxX+tysUT3L3qoZ9a RTuLJLASQj//Ycg2JFB4X8jCBVC8rTaTv/+ou5+jjJl98bUO4W74oj0ghdFP/CzB+UUTZK sV2lPIpF5ion3n4mLc5PiZdySngafhsq9WtLsLgbX/eTUODx2a9RiD+3L4b+Pw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1668443382; 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=wX56Rx4ehD7yCLYC+HBYrPWlmwQCTi9+gNx/cMRdAa0=; b=YSUY3x9QKkaBKpLI3HuYgJ3L+uxIygG746+BhVG6JRy2hyD9v0E6waIFwmYOUybnOdJ3Al G7H0jZldXWqYGJBA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH printk v4 20/39] console: introduce console_is_registered() Date: Mon, 14 Nov 2022 17:35:13 +0106 Message-Id: <20221114162932.141883-21-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" Currently it is not possible for drivers to detect if they have already successfully registered their console. Several drivers have multiple paths that lead to console registration. To avoid attempting a 2nd registration (which leads to a WARN), drivers are implementing their own solution. Introduce console_is_registered() so drivers can easily identify if their console is currently registered. A _locked() variant is also provided if the caller is already holding the console_list_lock. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- include/linux/console.h | 28 ++++++++++++++++++++++++++++ kernel/printk/printk.c | 2 +- 2 files changed, 29 insertions(+), 1 deletion(-) diff --git a/include/linux/console.h b/include/linux/console.h index c1ca461d088a..f716e1dd9eaf 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -228,6 +228,34 @@ static inline void console_srcu_write_flags(struct con= sole *con, short flags) WRITE_ONCE(con->flags, flags); } =20 +/* Variant of console_is_registered() when the console_list_lock is held. = */ +static inline bool console_is_registered_locked(const struct console *con) +{ + lockdep_assert_console_list_lock_held(); + return !hlist_unhashed(&con->node); +} + +/* + * console_is_registered - Check if the console is registered + * @con: struct console pointer of console to check + * + * Context: Process context. May sleep while acquiring console list lock. + * Return: true if the console is in the console list, otherwise false. + * + * If false is returned for a console that was previously registered, it + * can be assumed that the console's unregistration is fully completed, + * including the exit() callback after console list removal. + */ +static inline bool console_is_registered(const struct console *con) +{ + bool ret; + + console_list_lock(); + ret =3D console_is_registered_locked(con); + console_list_unlock(); + return ret; +} + /** * for_each_console_srcu() - Iterator over registered consoles * @con: struct console pointer used as loop cursor diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fb609a19f797..e770b1ede6c9 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3414,7 +3414,7 @@ static int unregister_console_locked(struct console *= console) /* Disable it unconditionally */ console_srcu_write_flags(console, console->flags & ~CON_ENABLED); =20 - if (hlist_unhashed(&console->node)) { + if (!console_is_registered_locked(console)) { console_unlock(); return -ENODEV; } --=20 2.30.2