From patchwork Tue Sep 21 10:33:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Lindgren X-Patchwork-Id: 12507557 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 5A678C433FE for ; Tue, 21 Sep 2021 10:33:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 410FE6112F for ; Tue, 21 Sep 2021 10:33:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231887AbhIUKfY (ORCPT ); Tue, 21 Sep 2021 06:35:24 -0400 Received: from muru.com ([72.249.23.125]:35518 "EHLO muru.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231823AbhIUKfY (ORCPT ); Tue, 21 Sep 2021 06:35:24 -0400 Received: from hillo.muru.com (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTP id 3FF7E8127; Tue, 21 Sep 2021 10:34:22 +0000 (UTC) From: Tony Lindgren To: Greg Kroah-Hartman Cc: Andy Shevchenko , Jiri Slaby , Johan Hovold , Vignesh Raghavendra , linux-serial@vger.kernel.org, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/6] n_tty: Start making use of -EAGAIN returned from process_output_block() Date: Tue, 21 Sep 2021 13:33:41 +0300 Message-Id: <20210921103346.64824-2-tony@atomide.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210921103346.64824-1-tony@atomide.com> References: <20210921103346.64824-1-tony@atomide.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org We check for -EAGAIN in n_tty_write() but never currently get it from process_output_block(). Let's add -EAGAIN handling and break out with 0 bytes processed. Note that if we return -EAGAIN from n_tty_write(), it will be treated as error by the caller rather than a retry. Looking at the patch description for commit 9ef8927f45f2 ("n_tty: check for negative and zero space return from tty_write_room") it looks like we have not made use of -EGAIN from process_output_block() so far, so this does not seem like it's currently needed as a fix. We can use -EAGAIN for serial layer power management changes as we now will make use of write_room() returning 0 for an idled serial port. Signed-off-by: Tony Lindgren --- drivers/tty/n_tty.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -549,6 +549,8 @@ static ssize_t process_output_block(struct tty_struct *tty, space = tty_write_room(tty); if (space <= 0) { mutex_unlock(&ldata->output_lock); + if (!space) + space = -EAGAIN; return space; } if (nr > space) @@ -2287,8 +2289,10 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, while (nr > 0) { ssize_t num = process_output_block(tty, b, nr); if (num < 0) { - if (num == -EAGAIN) - break; + if (num == -EAGAIN) { + retval = 0; + goto break_out; + } retval = num; goto break_out; }