From patchwork Wed Apr 21 09:54:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 426123 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 7D5CAC433ED for ; Wed, 21 Apr 2021 09:55:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48E2C61440 for ; Wed, 21 Apr 2021 09:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238751AbhDUJ4R (ORCPT ); Wed, 21 Apr 2021 05:56:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:52468 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238606AbhDUJ4J (ORCPT ); Wed, 21 Apr 2021 05:56:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8891061476; 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=DCcpn8+8l2aLtK9AKW5k1cue+Hn6i+5BhnYqOqX865Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y/Uqxr/3XQIK7l6SZGxOoi2Qz3BjbMM1tBBk3ygqwkm5ZCvVKQfCv0shfVEIGy97P 5BAxBQY7xCiJ5U4urr3md0qK0LIc3KbZ31wemq31TTqUbqiF21YJq+im5WUXeG+AaM J6eeaeOiIfeJxExebHoY3pwDtONJLjoh+tul9eg1c9Bug+fdRCOhBCLsOG+0rgminC qgus81vH9TcC5A1qeOp3Zs63c2O3RyB66NRTPoRRVS11lHTfnhDMwo53sEtVHVYBqT SKX1+Ibozc1EbfFMA8geFqkLJXddJAdxZUShLAkrmcauV0QxP8uMKR3aLx7GXnfNDz vxTBEtY60gJSg== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a7-0000ox-Qf; 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 13/26] serial: mcf: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:56 +0200 Message-Id: <20210421095509.3024-14-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 5275ad70fed3 ("tty: serial: mcf: 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/mcf.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/mcf.c b/drivers/tty/serial/mcf.c index 09c88c48fb7b..c7cec7d03620 100644 --- a/drivers/tty/serial/mcf.c +++ b/drivers/tty/serial/mcf.c @@ -319,9 +319,7 @@ static void mcf_rx_chars(struct mcf_uart *pp) uart_insert_char(port, status, MCFUART_USR_RXOVERRUN, ch, flag); } - spin_unlock(&port->lock); tty_flip_buffer_push(&port->state->port); - spin_lock(&port->lock); } /****************************************************************************/