From patchwork Wed Apr 21 09:54:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 425686 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 873BBC43600 for ; Wed, 21 Apr 2021 09:55:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5664E61449 for ; Wed, 21 Apr 2021 09:55:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238681AbhDUJ4L (ORCPT ); Wed, 21 Apr 2021 05:56:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:52328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238572AbhDUJ4J (ORCPT ); Wed, 21 Apr 2021 05:56:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 19EF861451; 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=cURs5qeivDO5gSpr3eXq9wzmT4dyWiefnPZY7i1667s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U+KYjIEvH9GgdfxZNZcO1DDWyZcnv8ddmk5RhHUdm6aSSIfNCEl9dSMUcPLgOageL 6IOlDbO0Qd3zBKHrDwQJYvUu5bULwmIazEH5oifM0WTISWEhcuS2gqAly+kY4yotZ7 L/j0ldBynmpxM7dLkvcnmk00bZdfonccanPiLEyEOgndL7/ZGNz0Sg7b0V3TtpxEZm 3JlcMmovw/f+I1Lk1rs0rIAtY1v7tRNZgwVp122u4n8vKuRfUoIsEjavj0ycmhXtFP HxXrzm4W1+j25Lu+qkvIh+XEBCBgIFyCdpPJHrnnPp8LYl5wEtL842xx7jHKSiTNfg MZi7rk96MtPlA== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a6-0000oR-Uu; Wed, 21 Apr 2021 11:55:38 +0200 From: Johan Hovold To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold , Tobias Klauser Subject: [PATCH 03/26] serial: altera_uart: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:46 +0200 Message-Id: <20210421095509.3024-4-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 dd085ed8ef6c ("tty: serial: altera: 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: Tobias Klauser Signed-off-by: Johan Hovold --- drivers/tty/serial/altera_uart.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c index 0e487ce091ac..7c5f4e966b59 100644 --- a/drivers/tty/serial/altera_uart.c +++ b/drivers/tty/serial/altera_uart.c @@ -243,9 +243,7 @@ static void altera_uart_rx_chars(struct altera_uart *pp) flag); } - spin_unlock(&port->lock); tty_flip_buffer_push(&port->state->port); - spin_lock(&port->lock); } static void altera_uart_tx_chars(struct altera_uart *pp)