From nobody Tue Apr 7 22:35:37 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 21238C433FE for ; Wed, 19 Oct 2022 15:07:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231446AbiJSPG7 (ORCPT ); Wed, 19 Oct 2022 11:06:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231894AbiJSPFn (ORCPT ); Wed, 19 Oct 2022 11:05:43 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87C3D2DC6 for ; Wed, 19 Oct 2022 07:59:21 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1666191381; 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=ERAmScBWw3AWOQd/N8KPYvjMNho4M2d8wqoVxvpkojg=; b=p7EHFUdVULSPTa08I7V4W4rGuOGZwbKXMbpmy7FQ/hM/Akq2VHbWOybQyOPaIOQrMynit4 ej7WV/9P69E8eZBOhLDiLJlrtilFtFK9XGJgoWlTrZNjwAdU/JWjcQgAlEaOPb4G1nWl5b TReEvqMia7ozppHpRIsh6OEWPdoTOkcPeJH4N8SEI0A/MzxlshaDMF13LQKP1TnMI+ubx9 Xl4NboHNjl6nuEPXtwS+kozYdOGmAF+ePdeob47Ak0wL6PRzU1obyGe39bWtW3Iy7oJVyD Vkv8yDL44DmJ8w3tppP5p/BE8zRaOFrxQ6dZE4JLY+ict0Hs+OTjbOcit2hpwA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1666191381; 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=ERAmScBWw3AWOQd/N8KPYvjMNho4M2d8wqoVxvpkojg=; b=XSBfRYfXfVmjl1gxZkSLwF2XwQJDPNi9TKXi2UryMFR1GEHWj2Cu4NTSvRskEHY/1hTm0t 8ZS0wYOq2I7A30BQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v2 37/38] printk: relieve console_lock of list synchronization duties Date: Wed, 19 Oct 2022 17:01:59 +0206 Message-Id: <20221019145600.1282823-38-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 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The console_list_lock provides synchronization for console list and console->flags updates. All call sites that were using the console_lock for this synchronization have either switched to use the console_list_lock or the SRCU list iterator. Remove console_lock usage for console list updates and console->flags updates. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- kernel/printk/printk.c | 21 +++++---------------- 1 file changed, 5 insertions(+), 16 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 3615ee6d68fd..840d581c4b23 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -82,8 +82,8 @@ EXPORT_SYMBOL(oops_in_progress); static DEFINE_MUTEX(console_mutex); =20 /* - * console_sem protects console_list and console->flags updates, and also - * provides serialization for access to the entire console driver system. + * console_sem protects updates to console->seq and console_suspended, + * and also provides serialization for console printing. */ static DEFINE_SEMAPHORE(console_sem); HLIST_HEAD(console_list); @@ -2635,7 +2635,7 @@ static int console_cpu_notify(unsigned int cpu) * console_lock - lock the console system for exclusive use. * * Acquires a lock which guarantees that the caller has - * exclusive access to the console system and console_list. + * exclusive access to the console system. * * Can sleep, returns nothing. */ @@ -2655,7 +2655,7 @@ EXPORT_SYMBOL(console_lock); * console_trylock - try to lock the console system for exclusive use. * * Try to acquire a lock which guarantees that the caller has exclusive - * access to the console system and console_list. + * access to the console system. * * returns 1 on success, and 0 on failure to acquire the lock. */ @@ -2911,8 +2911,7 @@ static bool console_flush_all(bool do_cond_resched, u= 64 *next_seq, bool *handove /** * console_unlock - unlock the console system * - * Releases the console_lock which the caller holds on the console system - * and the console driver list. + * Releases the console_lock which the caller holds on the console system. * * While the console_lock was held, console output may have been buffered * by printk(). If this is the case, console_unlock(); emits @@ -3098,9 +3097,7 @@ void console_stop(struct console *console) { __pr_flush(console, 1000, true); console_list_lock(); - console_lock(); console->flags &=3D ~CON_ENABLED; - console_unlock(); console_list_unlock(); =20 /* Ensure that all SRCU list walks have completed */ @@ -3111,9 +3108,7 @@ EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { console_list_lock(); - console_lock(); console->flags |=3D CON_ENABLED; - console_unlock(); console_list_unlock(); __pr_flush(console, 1000, true); } @@ -3315,7 +3310,6 @@ void register_console(struct console *newcon) * Put this console in the list - keep the * preferred driver at the head of the list. */ - console_lock(); if (hlist_empty(&console_list)) { /* Ensure CON_CONSDEV is always set for the head. */ newcon->flags |=3D CON_CONSDEV; @@ -3329,7 +3323,6 @@ void register_console(struct console *newcon) } else { hlist_add_behind_rcu(&newcon->node, console_list.first); } - console_unlock(); =20 /* No need to synchronize SRCU here! */ =20 @@ -3370,8 +3363,6 @@ static int unregister_console_locked(struct console *= console) if (res > 0) return 0; =20 - console_lock(); - /* Disable it unconditionally */ console->flags &=3D ~CON_ENABLED; =20 @@ -3394,8 +3385,6 @@ static int unregister_console_locked(struct console *= console) if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV) console_first()->flags |=3D CON_CONSDEV; =20 - console_unlock(); - /* Ensure that all SRCU list walks have completed */ synchronize_srcu(&console_srcu); =20 --=20 2.30.2