From patchwork Wed Apr 21 09:54:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 425683 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27B69C43619 for ; Wed, 21 Apr 2021 09:55:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F11AC61440 for ; Wed, 21 Apr 2021 09:55:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238716AbhDUJ4P (ORCPT ); Wed, 21 Apr 2021 05:56:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:52466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238605AbhDUJ4J (ORCPT ); Wed, 21 Apr 2021 05:56:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 734816143D; Wed, 21 Apr 2021 09:55:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618998936; bh=Xai30bPlo7ZkE9R0WT11XxAtQnG6hlhEwzXdh169xmo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ILjwThCJse63WRaNAKPK8maYE2RXBUt7zxNsB7XX6+MuCXQos3rHyG9EyROja2VYh 9dwWDP7v8jQLk0qcUbJTILB3oklyVh+OfUUkLHue3LWjhSdio0d9j2HACkkR4D6i2p 6ObE9g2/Z+fRyH91xmRufDB+aHLeGCr3Pj8hbu3pdDtiYHyR2put4WuDV+ZIhaS1WV DOG42B8Nz0EX0ndAJn8jgBpjVsVTwpCmXHYb2ruOytEuGAwRPAB65V/Npx+WL1mfle 36ueGzsN6i5hH7mPk8yjAGO8zhlPqVsTDV+Wj4cmSD9MNTqGoa73/m4TTTGPAyqoUy 4Qq0HiU1scpDg== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a7-0000ou-Nd; Wed, 21 Apr 2021 11:55:39 +0200 From: Johan Hovold To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold Subject: [PATCH 12/26] serial: lpc32xx_hs: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:55 +0200 Message-Id: <20210421095509.3024-13-johan@kernel.org> X-Mailer: git-send-email 2.26.3 In-Reply-To: <20210421095509.3024-1-johan@kernel.org> References: <20210421095509.3024-1-johan@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Commit ec128510905c ("tty: serial: lpc32xx_hs: drop uart_port->lock before calling tty_flip_buffer_push()") claimed to address a locking issue but only provided a dubious lockdep splat from an unrelated driver, which in the end turned out to be due a broken local change carried by the author. Unfortunately these patches were merged before the issue had been analysed properly so the commit messages makes no sense whatsoever. The real issue was first seen on RT which at the time effectively always set the low_latency flag for all serial drivers by patching tty_flip_buffer_push(). This in turn revealed that many drivers did not handle the infamous low_latency behaviour which meant that data was pushed immediately to the line discipline instead of being deferred to a work queue. Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"), tty_flip_buffer_push() always schedules a work item to push data to the line discipline and there's no need to keep any low_latency hacks around. Link: https://lore.kernel.org/linux-serial/cover.1376923198.git.viresh.kumar@linaro.org/ Signed-off-by: Johan Hovold --- drivers/tty/serial/lpc32xx_hs.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/lpc32xx_hs.c b/drivers/tty/serial/lpc32xx_hs.c index 1fa098d7aec4..b199d7859961 100644 --- a/drivers/tty/serial/lpc32xx_hs.c +++ b/drivers/tty/serial/lpc32xx_hs.c @@ -273,9 +273,7 @@ static void __serial_lpc32xx_rx(struct uart_port *port) tmp = readl(LPC32XX_HSUART_FIFO(port->membase)); } - spin_unlock(&port->lock); tty_flip_buffer_push(tport); - spin_lock(&port->lock); } static void __serial_lpc32xx_tx(struct uart_port *port)