From patchwork Wed Apr 21 09:55:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 425675 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, URIBL_BLOCKED, 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 E7532C43618 for ; Wed, 21 Apr 2021 09:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1CE56143D for ; Wed, 21 Apr 2021 09:55:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238804AbhDUJ4W (ORCPT ); Wed, 21 Apr 2021 05:56:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:52670 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238675AbhDUJ4K (ORCPT ); Wed, 21 Apr 2021 05:56:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8930E61462; Wed, 21 Apr 2021 09:55:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618998937; bh=JTOTZI6bMv68wR3qvzPPxYqwOcSxCiswzBee2Px7PgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DReJHcPysNeVifagY895TiF+h/2Zp6ioz4yTvg9tBr83wvF8cSx6hd4+zhbIQeaAb gWcaooTTNPRx1clPm1BZpluTZvUJtkNmhzzHm/6fXdMydcb2VRq3O9sMMtLBhKJhGU Mkb7myXJ/k7xuIksaV0msXrI9yrUyUJVxvdkUZJltZi7kNLuedrTIM0DfD44nvNtS6 oQJ02b4Cpc9BOqQ7vjdONUwS0Y5697+gM9TpJawkiz6inH4pH+v6b1/dsEMDLGntDU BnzlZgtPc4GJmDUX6+Gr+a3OKighfOCkXkphNu8z6OBauc2RK590cO8guaTukzM29D xpheRL5qWFzMw== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a8-0000ph-Pe; Wed, 21 Apr 2021 11:55:40 +0200 From: Johan Hovold To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold , Tony Prisk Subject: [PATCH 25/26] serial: vt8500: drop low-latency workaround Date: Wed, 21 Apr 2021 11:55:08 +0200 Message-Id: <20210421095509.3024-26-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 de49df58366f ("tty: serial: vt8500: 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/ Cc: Tony Prisk Signed-off-by: Johan Hovold --- drivers/tty/serial/vt8500_serial.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/vt8500_serial.c b/drivers/tty/serial/vt8500_serial.c index 764e992438b2..c5edd56ff830 100644 --- a/drivers/tty/serial/vt8500_serial.c +++ b/drivers/tty/serial/vt8500_serial.c @@ -184,9 +184,7 @@ static void handle_rx(struct uart_port *port) tty_insert_flip_char(tport, c, flag); } - spin_unlock(&port->lock); tty_flip_buffer_push(tport); - spin_lock(&port->lock); } static void handle_tx(struct uart_port *port)