From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E86BEC43334 for ; Mon, 4 Jul 2022 06:52:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232420AbiGDGv6 (ORCPT ); Mon, 4 Jul 2022 02:51:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbiGDGv5 (ORCPT ); Mon, 4 Jul 2022 02:51:57 -0400 Received: from mail-ej1-f42.google.com (mail-ej1-f42.google.com [209.85.218.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29C151A1; Sun, 3 Jul 2022 23:51:56 -0700 (PDT) Received: by mail-ej1-f42.google.com with SMTP id d2so15054568ejy.1; Sun, 03 Jul 2022 23:51:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=V3WLzRQE5hlj9Ag2r0vYMFsjKsgZON5RNX5KPeYiXww=; b=INexnmujA72hd1cSfEjJYi3EV6fpTDEUwkgIi6uIKB1St+EjgHcYc7RW5IM7bD6jyD uMB3fKl8wb41IHpcfhw4RC7aLboZ88PVtB0jt2IG2UfhV5eACroeHWvXzGVWxgyPWc3j /OWE2e8VG3cNmM+FDEvBcqTM1iHBrjFbywUPX6/mL2nvNQzYoRNbS4FOFfi3dp8d9sHf XuDXqMDzvOc1KjM3gJc7PyhFwvnOHasVnDc7mbF3O3XV/qbg/B1k62Yisa0kDqP9J52T /QTYjf9Q3H1E4138ac1yLuyY+wA10WmQ/RAEMiHQ9tGnJgnpVse56XCLxMjhsTSZnkb0 il4w== X-Gm-Message-State: AJIora+TLmBlC85CkcbaIpMzCp2o4sczhnwP5AIwyrpl/+3/O1ZGsrCg DA5kzOZA0u2UNLBcrwqCITw= X-Google-Smtp-Source: AGRyM1v8dChAQI8X41cjbxblEKGrrl0gDwkuRmFOZKgWiz0FHKJWfFar01jZsrywV4UoVL2Tkx3+Ww== X-Received: by 2002:a17:906:8315:b0:726:38da:f0f with SMTP id j21-20020a170906831500b0072638da0f0fmr27302882ejx.462.1656917514750; Sun, 03 Jul 2022 23:51:54 -0700 (PDT) Received: from ?IPV6:2a0b:e7c0:0:107::49? ([2a0b:e7c0:0:107::49]) by smtp.gmail.com with ESMTPSA id q16-20020a056402249000b00438a13508c4sm8472754eda.51.2022.07.03.23.51.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 03 Jul 2022 23:51:54 -0700 (PDT) Message-ID: <60678c81-27bf-6f37-bae5-ccc91d714204@kernel.org> Date: Mon, 4 Jul 2022 08:51:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v9 4/6] serial: take termios_rwsem for ->rs485_config() & pass termios as param Content-Language: en-US To: =?UTF-8?Q?Ilpo_J=c3=a4rvinen?= , linux-serial@vger.kernel.org, Greg KH , Andy Shevchenko , Vladimir Zapolskiy , Russell King , Richard Genoud , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , Maxime Coquelin , Alexandre Torgue , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com Cc: Lukas Wunner , =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= , Lino Sanfilippo References: <20220624204210.11112-1-ilpo.jarvinen@linux.intel.com> <20220624204210.11112-5-ilpo.jarvinen@linux.intel.com> From: Jiri Slaby In-Reply-To: <20220624204210.11112-5-ilpo.jarvinen@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24. 06. 22, 22:42, Ilpo Järvinen wrote: > To be able to alter ADDRB within ->rs485_config(), take termios_rwsem > before calling ->rs485_config() and pass termios. OK, FTR, worth noting the tty->termios_rwsem -> port->mutex lock chain is preexisting. Anyway, I'm not sure I buy the above. Why is termios_rwsem needed to alter ADDRB? > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > index 621fc15e2e54..44c3785445e3 100644 > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c ... > @@ -1511,6 +1511,10 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg) > if (ret != -ENOIOCTLCMD) > goto out; > > + /* rs485_config requires more locking than others */ > + if (cmd == TIOCGRS485) > + down_write(&tty->termios_rwsem); > + > mutex_lock(&port->mutex); > uport = uart_port_check(state); > ... > @@ -1551,6 +1555,8 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg) > } > out_up: > mutex_unlock(&port->mutex); > + if (cmd == TIOCGRS485) > + up_write(&tty->termios_rwsem); > out: > return ret; > } thanks, -- js