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[2620:137:e000::1:20]) by mx.google.com with ESMTP id q14-20020a056402040e00b0045d8bff7b1asi7003968edv.403.2022.10.19.08.11.04; Wed, 19 Oct 2022 08:11:30 -0700 (PDT) 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=odMAd6jZ; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e; 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 S231927AbiJSPGf (ORCPT + 99 others); Wed, 19 Oct 2022 11:06:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231835AbiJSPFk (ORCPT ); Wed, 19 Oct 2022 11:05:40 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EB4B13D0F for ; Wed, 19 Oct 2022 07:59:09 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1666191375; 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=Rxx7a00tnCHfnWXA978Xi0IL/mfHFWoLJumPfZjxuVQ=; b=odMAd6jZuExx16Yi0L8xd1hm9Jh9VTjUOvjUUgrX8qFZQuCWOzfAaZvh89StL/uY5ZVjZ4 7F0py/hns3GzhNljNb4CSr+P5RvwEKeVFVSo7ucX0apDwGWsb+zxnCp4263f8YKJ9a5ej1 2rV6t+eru8+PT568/dvEv0WiF4bn/adCAwyLxplBuLF8aZHWoHD+n5evDi2JVgnqY8rjNr Pt3sSFfwb1FV+WRk5mWlhtAOGR/p0dm76Sw3rc+OGGbhM33YJGS18mUoUTGARbsvXP77z4 CFsQZ+FmootigSKYJ31Vjh5hqGF6+j1S9tpl8U4eAuAup1tordjr0REfQ7pl7A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1666191375; 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=Rxx7a00tnCHfnWXA978Xi0IL/mfHFWoLJumPfZjxuVQ=; b=q9rIFA276lgWZLXV5mkpOktuUZD6YWke7bg19dKAJViyJu9A6OrFIkzYrQzLJ2n8EtnLIQ id3MWXWGrsWj0ZDA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH printk v2 23/38] tty: tty_io: document console_lock usage Date: Wed, 19 Oct 2022 17:01:45 +0206 Message-Id: <20221019145600.1282823-24-john.ogness@linutronix.de> In-Reply-To: <20221019145600.1282823-1-john.ogness@linutronix.de> References: <20221019145600.1282823-1-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?1747129247991016914?= X-GMAIL-MSGID: =?utf-8?q?1747129247991016914?= 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: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 2050e63963bb..333579bfa335 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3526,6 +3526,14 @@ 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. + * + * Stop console printing because the device() callback may + * assume the console is not within its write() callback. + */ console_lock(); for_each_console(c) { if (!c->device)