From patchwork Wed Apr 21 09:54:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 426126 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 C3B4DC43616 for ; Wed, 21 Apr 2021 09:55:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 985676008E for ; Wed, 21 Apr 2021 09:55:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238700AbhDUJ4O (ORCPT ); Wed, 21 Apr 2021 05:56:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:52428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238595AbhDUJ4J (ORCPT ); Wed, 21 Apr 2021 05:56:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1749361450; 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=//83zS1ZBhRXsUePF94O/LAAvE4gdmM6NVLpqE0AkyQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=trZ3ds7ezLkR0FwnVus7VJD54aK3VeejKJg7SLDa6DmE+vKFah6CDg2kKCsy1AhTj la+Nrl/xQqdpOZ/a2ZZ1U3Ahc4eRWBI6LYauernDB2hJQk5wu0xukCyCDOnmx3JXZq Zk0UhvZlUQAbwMiGu4gWv9iwnnsrisNv7IZY+q2jiFe638UAZ5BjYOOo0NWb92yXUW lV+rbrWx2EeVhk3Z+5WioiWCHXlX2qcP2ru5zCVwhYdEYoadvZ45dNj0O5gHgHqfi3 4R4eAhO7YRaUhthQ4SKaSrk/dfoRIKkb+itzKKANIDKapE0yfC7V9be7MFkD1TwWUH bwOPWsGFDaiKQ== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a7-0000ob-7O; 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 06/26] serial: apbuart: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:49 +0200 Message-Id: <20210421095509.3024-7-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 78d34d75c84d ("tty: serial: apbuart: 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/apbuart.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/apbuart.c b/drivers/tty/serial/apbuart.c index e8d56e899ec7..d8c937bdf3f9 100644 --- a/drivers/tty/serial/apbuart.c +++ b/drivers/tty/serial/apbuart.c @@ -117,9 +117,7 @@ static void apbuart_rx_chars(struct uart_port *port) status = UART_GET_STATUS(port); } - spin_unlock(&port->lock); tty_flip_buffer_push(&port->state->port); - spin_lock(&port->lock); } static void apbuart_tx_chars(struct uart_port *port)