From patchwork Thu May 25 09:31:57 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 686351 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 1FA00C77B7A for ; Thu, 25 May 2023 09:35:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240618AbjEYJfI (ORCPT ); Thu, 25 May 2023 05:35:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240627AbjEYJel (ORCPT ); Thu, 25 May 2023 05:34:41 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 074271B1; Thu, 25 May 2023 02:34:33 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1685007270; 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=nPDJHm4lU4uW5PYPRilpSR3PUXlYNGeyc1k5gm2WMrg=; b=Bn9RR6tFw4VHxMRtNu5ITPrZWhJi9VsTk3Ief2f7HcBlEtLMBnVNouWr0IM4OCsP02Dq7Q gdWxPPKFD6kokGHfylzCLf1elFujWvrjGvnJqujbqfHuADfuMLyd6ENik68sarNNrhQFuE c4RkxSMLo7Jg4Ctn+oJapV4snGobAEx0h5zm/6LKkgV48KMBlXtUQ7u4cf07BFSCaEYVjs CLVHT/h0C+zTSycU3IFxqCaSwRZY02Qgl4LpRpu15aLv5QBON8m6QA+BXf3T7MUmdcMh/v tARTQSo+S9rmvPFdJm8rCofDsynBzdEdXV+R9vlJp9w5Fe5d9Bc6DCZitRM3iw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1685007270; 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=nPDJHm4lU4uW5PYPRilpSR3PUXlYNGeyc1k5gm2WMrg=; b=D7c8sfO9B0xWafdKccZQxoeJ+NYAiCmP6zJoGfo+FNhKFSWjUhH4xcqrDjjtHasOyuCFUa o6+70hF7B7N+QMDA== To: Greg Kroah-Hartman Cc: Petr Mladek , Thomas Gleixner , linux-kernel@vger.kernel.org, Jiri Slaby , =?utf-8?q?Ilpo_J=C3=A4rvinen?= , Tony Lindgren , Lukas Wunner , Matthias Schiffer , linux-serial@vger.kernel.org Subject: [PATCH tty v1 6/8] serial: 8250: lock port for omap8250_restore_regs() Date: Thu, 25 May 2023 11:37:57 +0206 Message-Id: <20230525093159.223817-7-john.ogness@linutronix.de> In-Reply-To: <20230525093159.223817-1-john.ogness@linutronix.de> References: <20230525093159.223817-1-john.ogness@linutronix.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org omap8250_restore_regs() accesses UART_IER. This register is modified twice by each console write (serial8250_console_write()) under the port lock. However, not all calls to omap8250_restore_regs() are under the port lock. Add the missing port locking around omap8250_restore_regs() calls. Add lockdep notation to the omap8250_restore_regs(). Note that this is not fixing a real problem because the serial devices are resumed before console printing is enabled. However, adding this locking allows for clean locking semantics for omap8250_restore_regs() so that lockdep can be used to identify possible problems in the future. It also simplifies synchronization of UART_IER in general by not needing to rely on such implementation details. Signed-off-by: John Ogness --- drivers/tty/serial/8250/8250_omap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 3cb9cfa62331..34939462fd69 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -309,6 +309,9 @@ static void omap8250_restore_regs(struct uart_8250_port *up) struct uart_8250_dma *dma = up->dma; u8 mcr = serial8250_in_MCR(up); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + if (dma && dma->tx_running) { /* * TCSANOW requests the change to occur immediately however if @@ -1739,8 +1742,11 @@ static int omap8250_runtime_resume(struct device *dev) if (priv->line >= 0) up = serial8250_get_port(priv->line); - if (up && omap8250_lost_context(up)) + if (up && omap8250_lost_context(up)) { + spin_lock_irq(&up->port.lock); omap8250_restore_regs(up); + spin_unlock_irq(&up->port.lock); + } if (up && up->dma && up->dma->rxchan && !(priv->habit & UART_HAS_EFR2)) { spin_lock_irq(&up->port.lock);