From patchwork Wed Apr 21 09:55:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 426119 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 D5025C4363C for ; Wed, 21 Apr 2021 09:55:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A774E61440 for ; Wed, 21 Apr 2021 09:55:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238777AbhDUJ4T (ORCPT ); Wed, 21 Apr 2021 05:56:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:52604 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238640AbhDUJ4K (ORCPT ); Wed, 21 Apr 2021 05:56:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 11FCF61581; 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=YKMnP0+4p6GKexVrNEN7sv2xmhyZgFqSF1QOLT/GVgE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uL9yfpCPXLBNkbfnvYL+7d8+lEQIo7kRyvRKzPgiiZmsKe50beZDA5i7+HfVzpdtV 72ziLDAsCe1eiJAPNFGVjwdyvAhv2wO0F8dRRerOdJi4Lrtu07rftNPOj2YC+7+nfo u8rI8UZeXZavmpnGq/hDcv1goSXtL+zyiZWd+fhTgDJohsEHRd28rKynVhIQ8LYcKb mIy3gV8es3gb1s70+ZG63dwgXdxZJV3DsdftXM3GRZAU7sXhYJez/NOvwJ8fi86yUf AH7Z1B3pQULBUxph/CoSdS4QDjCn0GlvCdi+VWdfYl5BXgh4F4pmLiNyWD6KVzIfUL u5319UUw4TwPQ== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a8-0000pF-AW; 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 , Kevin Cernekee Subject: [PATCH 19/26] serial: rp2: drop low-latency workaround Date: Wed, 21 Apr 2021 11:55:02 +0200 Message-Id: <20210421095509.3024-20-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 de7053c77123 ("tty: serial: rp2: 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: Kevin Cernekee Signed-off-by: Johan Hovold --- drivers/tty/serial/rp2.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c index 5690c09cc041..d60abffab70e 100644 --- a/drivers/tty/serial/rp2.c +++ b/drivers/tty/serial/rp2.c @@ -424,9 +424,7 @@ static void rp2_rx_chars(struct rp2_uart_port *up) up->port.icount.rx++; } - spin_unlock(&up->port.lock); tty_flip_buffer_push(port); - spin_lock(&up->port.lock); } static void rp2_tx_chars(struct rp2_uart_port *up)