From patchwork Wed Apr 21 09:54:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 426125 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 5B527C43617 for ; Wed, 21 Apr 2021 09:55:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2419D61448 for ; Wed, 21 Apr 2021 09:55:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238698AbhDUJ4N (ORCPT ); Wed, 21 Apr 2021 05:56:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:52430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238583AbhDUJ4J (ORCPT ); Wed, 21 Apr 2021 05:56:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1CB6A6144F; 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=dLdHsb0G5vHHwinxbCFbMP5LZuwkh8IRJ8RB0D4Yqzw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P5riJqE6OIsWtN/+3NKWPNr9jKi1Gj43LxlGFNQN1T60or2LGD0HiUSQAfVi6v3CE YV45JGK2dsRqBu6zQsyS+gxfILfis/j9uNH0f1yfX2z2654qob8uMaeRAT6Tc/l0MR ogh/wI97yp5WlaVBcvUsfgZIBfgD+mYevx2IqUXTOQTLy7sA5bTTsX6neaL++ZaSIW c/G+pjsugHpFs7ZZKAI5+K4zYyzvpfBGKR+3Z1/jPWQ7vcz47fGNUcuHWzMeTp+4Ub 8Ep6tP+GOgjxLLG5TU4U++OqmGYV3219MYPxUDOn3e/9GtT1iHbs/4g9a7phDVHWWP 3OFScldzFMxUA== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a7-0000oe-9s; 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 07/26] serial: ar933x: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:50 +0200 Message-Id: <20210421095509.3024-8-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 b16c8e3eed12 ("tty: serial: ar933x: 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/ar933x_uart.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c index c2be7cf91399..4379ca4842ae 100644 --- a/drivers/tty/serial/ar933x_uart.c +++ b/drivers/tty/serial/ar933x_uart.c @@ -385,9 +385,7 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up) tty_insert_flip_char(port, ch, TTY_NORMAL); } while (max_count-- > 0); - spin_unlock(&up->port.lock); tty_flip_buffer_push(port); - spin_lock(&up->port.lock); } static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)