From patchwork Wed Apr 21 09:54:53 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johan Hovold X-Patchwork-Id: 425676 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 A3E42C433B4 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 67F4361456 for ; Wed, 21 Apr 2021 09:55:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238774AbhDUJ4T (ORCPT ); Wed, 21 Apr 2021 05:56:19 -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 S238644AbhDUJ4K (ORCPT ); Wed, 21 Apr 2021 05:56:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1925C61582; 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=Ksv9YjFjtrxObzx24ubHLCHYQzR97rDs6O9O5M32Y9E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xo+gdLo0wZl88+ZIU9ETD9DQj6nAHMGqRZR2vfMBWax16YBxqPkVI5VMNVSWs4qnK Zd4TWxWiHjicP+wl+WqBseoTfB4K21KLh3erQaiCWT/opq0Ek42jQzGJ9C2ipNBZ4x mSImIylqi+06i72GoMQ74cmWFMJLCP/Jlxyv5bz0qpboJvHV67JhAQW3w6eQPKYShW t99UXt06Pdfx3CcuXE5kzQlSvJkCZsA4Jv1n+PEJR5a/cqXgJ18FPaOHZif8jZhNdV 05T6y+XIcK+EA9GMTMDaaJhbaI5ZIEYxWTOnQtOqKMi6KAajDBNdKlYJz5j3VEoI3K cxsKw49p2AxRQ== Received: from johan by xi.lan with local (Exim 4.93.0.4) (envelope-from ) id 1lZ9a7-0000on-Hf; 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 10/26] serial: bcm63xx: drop low-latency workaround Date: Wed, 21 Apr 2021 11:54:53 +0200 Message-Id: <20210421095509.3024-11-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 b4d499241c34 ("tty: serial: bcm63xx: 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/bcm63xx_uart.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/bcm63xx_uart.c b/drivers/tty/serial/bcm63xx_uart.c index 5674da2b76f0..5fb0e84f7fd1 100644 --- a/drivers/tty/serial/bcm63xx_uart.c +++ b/drivers/tty/serial/bcm63xx_uart.c @@ -294,9 +294,7 @@ static void bcm_uart_do_rx(struct uart_port *port) } while (--max_count); - spin_unlock(&port->lock); tty_flip_buffer_push(tty_port); - spin_lock(&port->lock); } /*