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[2620:137:e000::1:20]) by mx.google.com with ESMTP id 194-20020a6304cb000000b00429f2cb4a47si11758295pge.491.2022.11.07.06.21.02; Mon, 07 Nov 2022 06:21:15 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=0d3z4xL9; dkim=neutral (no key) header.i=@linutronix.de; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232291AbiKGORw (ORCPT + 99 others); Mon, 7 Nov 2022 09:17:52 -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 S231968AbiKGOQu (ORCPT ); Mon, 7 Nov 2022 09:16:50 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC67A1D0DC for ; Mon, 7 Nov 2022 06:16:47 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1667830606; 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=dCcbZ2nZRP4FMVS4VfHiFcW5Scqwo3VptQivrT22/cY=; b=0d3z4xL9MeTeQrkMA1tq1zT9HmredXjKfiAbW7rrtu69ZIzka1gnMp40KPeuojsXX3Nkr9 AZxEtIcS7R2Ezc3gu9mFGy9bLznQxPV/GWpN/5heML3RCJIhOWSZv8V9MjC7lsI0wd9e4w jJrKKPKFlBps/DuPHb/J6jyDYiVm/RAPKUHiuA97ydwbA48kWnvVAHxZSQJhkwrEbnwRid ZLi2s1anaVF8BNNITWyPc3TywgJZJ9i0QoavNfJPeAPqEd5YQiPxGJfXjBt/6dkKiPkbZQ GHGshCC10unhBdwLm/cN9x56+2c6GzWHyDc1YV49NuVb+3+IcBcubRxsqwUzqQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1667830606; 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=dCcbZ2nZRP4FMVS4VfHiFcW5Scqwo3VptQivrT22/cY=; b=0BuRCrFb1lOtnGXdQk8YdKfvXzno2vWMkwrUfCthAamtrK5DjD0g+Mn8fyVA3k00ypBjwd hS7Z8rzULOsYtMBA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH printk v3 13/40] tty: tty_io: document console_lock usage Date: Mon, 7 Nov 2022 15:22:11 +0106 Message-Id: <20221107141638.3790965-14-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 X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INVALID_DATE_TZ_ABSURD, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748847428067657017?= X-GMAIL-MSGID: =?utf-8?q?1748847428067657017?= 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 = 0; + /* + * 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)