From patchwork Wed Apr 21 09:55:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 425677 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 39C3AC4361B for ; Wed, 21 Apr 2021 09:55:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 065DD6143D for ; Wed, 21 Apr 2021 09:55:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238780AbhDUJ4T (ORCPT ); Wed, 21 Apr 2021 05:56:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:52654 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238647AbhDUJ4K (ORCPT ); Wed, 21 Apr 2021 05:56:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 18EE961452; 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=Iu7STYqQoU25QYwNxiMypzgo5dwXaP/UJ6w1NJlXkQI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PLJO3cVFkPvKUo0Jduizeba4+6ayZsxmcc/n50l4xFf3AU88OHclO6VGmscdSBlqW huksUBwxPuBAknROGVI+CIfCAFChiwPD5C/CwOFyONQbL55n1R8pnUzhNdrYjqpeUK kDtbfWhPNgqnN7N2S6RcRvycthE8hkRPY/L8VgswDSye9LXrLCi/T8DQVocLez8Tkl 1Xh9Fmf1R7p3iQt7dM6+IcfKlxSPEOPK5P0PkWmDkaUV1R8TY+gHSoAThOLn+W+tuC uWPbsGWVm2AQIZv255y0rg877JWullgu6BQJ15WNrncZYplar1Z1uHwM6DFSLLv2cV HnX1eg1Ph2jlw== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a8-0000pI-D1; 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 Subject: [PATCH 20/26] serial: sa1100: drop low-latency workaround Date: Wed, 21 Apr 2021 11:55:03 +0200 Message-Id: <20210421095509.3024-21-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 53e0e6706c76 ("tty: serial: sa1100: 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/sa1100.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c index f5fab1dd96bc..697b6a002a16 100644 --- a/drivers/tty/serial/sa1100.c +++ b/drivers/tty/serial/sa1100.c @@ -223,9 +223,7 @@ sa1100_rx_chars(struct sa1100_port *sport) UTSR0_TO_SM(UART_GET_UTSR0(sport)); } - spin_unlock(&sport->port.lock); tty_flip_buffer_push(&sport->port.state->port); - spin_lock(&sport->port.lock); } static void sa1100_tx_chars(struct sa1100_port *sport)