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[2620:137:e000::1:20]) by mx.google.com with ESMTP id b10-20020a6567ca000000b0050126b5d089si166953pgs.386.2023.03.02.12.00.02; Thu, 02 Mar 2023 12:00:21 -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=t7LjSSSE; 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 S230149AbjCBT6I (ORCPT + 99 others); Thu, 2 Mar 2023 14:58:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229805AbjCBT5q (ORCPT ); Thu, 2 Mar 2023 14:57:46 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3CEE474E3 for ; Thu, 2 Mar 2023 11:57:44 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1677787063; 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=R9tOYyS2PzrZZNPqHz2RZVi/VNmEwSgQ/BXnraEltaw=; b=t7LjSSSEITvx8kbiv5CVXv2TXdNm6VXkiTcPhTMnFJX4uIr7wF06FV5+xsBpNoi8RF6APL UO2YbBOrbzGF/RMFHD+y8k1VuMeEzXW42wTe98I556VXsXrPWorh0w3dwAcO2Rwf4Vxgkd I3enyGsYKtohM4C8uiKqw3hL//CQ8usus0d4Il4sQZK30JSxgfQ8QbCpygTMbOsDtRJTeJ Fk+vKkKIejQ3e6s8f8TnxJ/kazi1uJky+fO9DpowvQunD4NR/+aCzJ+p7peDZ37PlzKSH9 mCK0vzr1g86tZ39IPMVc2Vo3iU3nFyewTWe7vUwFXdm+rNqrX4szqlm9ejBNtA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1677787063; 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=R9tOYyS2PzrZZNPqHz2RZVi/VNmEwSgQ/BXnraEltaw=; b=JM39akAot7pRoHec+7jJQXSabDYbtHF8CZ6R6xuPk+UspGwDe0FQfGbU+lqt/abGpZprEb eBv9KM06PZPGPvDA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH printk v1 04/18] printk: Add per-console suspended state Date: Thu, 2 Mar 2023 21:02:04 +0106 Message-Id: <20230302195618.156940-5-john.ogness@linutronix.de> In-Reply-To: <20230302195618.156940-1-john.ogness@linutronix.de> References: <20230302195618.156940-1-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?1759287414045440871?= X-GMAIL-MSGID: =?utf-8?q?1759287414045440871?= Currently the global @console_suspended is used to determine if consoles are in a suspended state. Its primary purpose is to allow usage of the console_lock when suspended without causing console printing. It is synchronized by the console_lock. Rather than relying on the console_lock to determine suspended state, make it an official per-console state that is set within console->flags. This allows the state to be queried via SRCU. @console_suspended will continue to exist, but now only to implement the console_lock/console_unlock trickery and _not_ to represent the suspend state of a particular console. Signed-off-by: John Ogness --- include/linux/console.h | 3 +++ kernel/printk/printk.c | 46 ++++++++++++++++++++++++++++++++--------- 2 files changed, 39 insertions(+), 10 deletions(-) diff --git a/include/linux/console.h b/include/linux/console.h index 1e36958aa656..f7967fb238e0 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -153,6 +153,8 @@ static inline int con_debug_leave(void) * receiving the printk spam for obvious reasons. * @CON_EXTENDED: The console supports the extended output format of * /dev/kmesg which requires a larger output buffer. + * @CON_SUSPENDED: Indicates if a console is suspended. If true, the + * printing callbacks must not be called. */ enum cons_flags { CON_PRINTBUFFER = BIT(0), @@ -162,6 +164,7 @@ enum cons_flags { CON_ANYTIME = BIT(4), CON_BRL = BIT(5), CON_EXTENDED = BIT(6), + CON_SUSPENDED = BIT(7), }; /** diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index bdeaf12e0bd2..626d467c7e9b 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2563,10 +2563,26 @@ MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to hig */ void suspend_console(void) { + struct console *con; + if (!console_suspend_enabled) return; pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); pr_flush(1000, true); + + console_list_lock(); + for_each_console(con) + console_srcu_write_flags(con, con->flags | CON_SUSPENDED); + console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. All printing + * contexts must be able to see that they are suspended so that it + * is guaranteed that all printing has stopped when this function + * completes. + */ + synchronize_srcu(&console_srcu); + console_lock(); console_suspended = 1; up_console_sem(); @@ -2574,11 +2590,26 @@ void suspend_console(void) void resume_console(void) { + struct console *con; + if (!console_suspend_enabled) return; down_console_sem(); console_suspended = 0; console_unlock(); + + console_list_lock(); + for_each_console(con) + console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED); + console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. All printing + * contexts must be able to see they are no longer suspended so + * that they are guaranteed to wake up and resume printing. + */ + synchronize_srcu(&console_srcu); + pr_flush(1000, true); } @@ -2681,6 +2712,9 @@ static inline bool console_is_usable(struct console *con) if (!(flags & CON_ENABLED)) return false; + if ((flags & CON_SUSPENDED)) + return false; + if (!con->write) return false; @@ -3695,8 +3729,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre /* * Hold the console_lock to guarantee safe access to - * console->seq and to prevent changes to @console_suspended - * until all consoles have been processed. + * console->seq. */ console_lock(); @@ -3712,14 +3745,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre } console_srcu_read_unlock(cookie); - /* - * If consoles are suspended, it cannot be expected that they - * make forward progress, so timeout immediately. @diff is - * still used to return a valid flush status. - */ - if (console_suspended) - remaining = 0; - else if (diff != last_diff && reset_on_progress) + if (diff != last_diff && reset_on_progress) remaining = timeout_ms; console_unlock();